Syncing Things
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@ -1,32 +1,76 @@
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package matrix
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import "strings"
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import (
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"errors"
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"strconv"
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"strings"
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)
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// Matrix is a grid of ints
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type Matrix struct {
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vals [][]int
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}
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// New creates a new Matrix from a string of numbers
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func New(in string) (*Matrix, error) {
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ret := Matrix{}
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rows := strings.Split(in, "\n")
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for i := range rows {
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flds := strings.Fields(rows[i])
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var ints []int
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for j := range flds {
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if v, err := strconv.Atoi(flds[j]); err != nil {
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return &ret, err
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} else {
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ints = append(ints, v)
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}
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}
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ret.vals = append(ret.vals, ints)
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}
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numInRow := -1
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for i := range ret.vals {
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if numInRow != -1 {
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if len(ret.vals[i]) != numInRow {
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return &ret, errors.New("All rows must be equal length")
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}
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}
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numInRow = len(ret.vals[i])
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}
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return &ret, nil
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}
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// Rows returns the values of the rows in the matrix
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func (m *Matrix) Rows() [][]int {
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return m.vals
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}
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func (m *Matrix) Cols() [][]int {
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ret := [][]int{}
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if len(m.vals) > 0 {
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// for i := 0; i < len(m.vals[0]); i++ {
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// }
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var ret [][]int
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for i := range m.vals {
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var row []int
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for j := range m.vals[i] {
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row = append(row, m.vals[i][j])
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}
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ret = append(ret, row)
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}
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return ret
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}
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// Cols returns the values of the cols in the matrix
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func (m *Matrix) Cols() [][]int {
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var ret [][]int
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for i := range m.vals[0] {
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var row []int
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for j := range m.vals {
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row = append(row, m.vals[j][i])
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}
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ret = append(ret, row)
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}
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return ret
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}
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// Set sets the value at r,c to val
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func (m *Matrix) Set(r, c int, val int) bool {
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if len(m.vals) < r || len(m.vals[r]) < c {
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if r < 0 || c < 0 {
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return false
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}
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if len(m.vals) <= r || len(m.vals[r]) <= c {
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return false
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}
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m.vals[r][c] = val
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@ -0,0 +1,45 @@
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# Saddle Points
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Write a program that detects saddle points in a matrix.
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So say you have a matrix like so:
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```plain
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0 1 2
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|---------
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0 | 9 8 7
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1 | 5 3 2 <--- saddle point at (1,0)
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2 | 6 6 7
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```
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It has a saddle point at (1, 0).
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It's called a "saddle point" because it is greater than or equal to
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every element in its row and the less than or equal to every element in
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its column.
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A matrix may have zero or more saddle points.
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Your code should be able to provide the (possibly empty) list of all the
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saddle points for any given matrix.
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Note that you may find other definitions of matrix saddle points online,
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but the tests for this exercise follow the above unambiguous definition.
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To run the tests simply run the command `go test` in the exercise directory.
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If the test suite contains benchmarks, you can run these with the `-bench`
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flag:
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go test -bench .
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For more detailed info about the Go track see the [help
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page](http://exercism.io/languages/go).
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## Source
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J Dalbey's Programming Practice problems [http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html](http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html)
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## Submitting Incomplete Problems
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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@ -0,0 +1,109 @@
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package matrix
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import (
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"errors"
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"fmt"
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"strconv"
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"strings"
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)
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// Matrix is a grid of ints
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type Matrix struct {
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vals [][]int
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}
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type Pair [2]int
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// New creates a new Matrix from a string of numbers
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func New(in string) (*Matrix, error) {
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ret := Matrix{}
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rows := strings.Split(in, "\n")
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for i := range rows {
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flds := strings.Fields(rows[i])
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var ints []int
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for j := range flds {
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if v, err := strconv.Atoi(flds[j]); err != nil {
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return &ret, err
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} else {
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ints = append(ints, v)
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}
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}
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ret.vals = append(ret.vals, ints)
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}
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numInRow := -1
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for i := range ret.vals {
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if numInRow != -1 {
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if len(ret.vals[i]) != numInRow {
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return &ret, errors.New("All rows must be equal length")
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}
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}
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numInRow = len(ret.vals[i])
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}
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return &ret, nil
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}
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func (m *Matrix) Saddle() []Pair {
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var ret []Pair
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// We're going to get a list of coords for row highs
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// then compare that to a list of coords for col lows
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var testRows []Pair
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for i := range m.vals {
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testRows = append(testRows, Pair{i, m.findRowHigh(i)})
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}
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fmt.Println(testRows)
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return ret
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for j := range m.vals[0] {
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v := Pair{m.findColLow(j), j}
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// If this pair is in testRows, it's a saddle point
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for i := range testRows {
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if v[0] == testRows[i][0] && v[1] == testRows[i][1] {
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ret = append(ret, v)
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}
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}
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}
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return ret
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}
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// Cols returns the values of the cols in the matrix
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func (m *Matrix) Cols() [][]int {
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var ret [][]int
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for i := range m.vals[0] {
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var row []int
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for j := range m.vals {
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row = append(row, m.vals[j][i])
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}
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ret = append(ret, row)
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}
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return ret
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}
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// findColLow finds the lowest value in a column
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func (m *Matrix) findColLow(c int) int {
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cols := m.Cols()
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var idx int
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val := -1
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if c >= 0 && c < len(cols) {
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for i := range cols[c] {
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if cols[c][i] < val || val == -1 {
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val = cols[c][i]
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idx = i
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}
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}
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}
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return idx
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}
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// findColLow finds the lowest value in a column
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func (m *Matrix) findRowHigh(r int) int {
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var idx int
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val := -1
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if r >= 0 && r < len(m.vals) {
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for i := range m.vals[r] {
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if m.vals[r][i] < val || val == -1 {
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val = m.vals[r][i]
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idx = i
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}
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}
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}
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return idx
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}
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@ -0,0 +1,67 @@
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// Short cut! Have you already done the matrix exercise?
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// If it seems helpful, copy your code from the matrix exercise
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// to this directory so you have access to it. You can leave it as matrix.go
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// and start a new file saddle_points.go with additional code that completes
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// this exercise. Submit only saddle_points.go for this exercise.
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package matrix
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import "testing"
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var tests = []struct {
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m string
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sp []Pair
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}{
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{"2 1\n1 2", nil},
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{"1 2\n3 4", []Pair{{0, 1}}},
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{"18 3 39 19 91\n38 10 8 77 320\n3 4 8 6 7", []Pair{{2, 2}}},
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{"4 5 4\n3 5 5\n1 5 4", []Pair{{0, 1}, {1, 1}, {2, 1}}},
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}
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func TestSaddle(t *testing.T) {
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for _, test := range tests {
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m, err := New(test.m)
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if err != nil {
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t.Fatalf("TestSaddle needs working New. "+
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"New(%s) returned %s. Error not expected.",
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test.m, err)
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}
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if sp := m.Saddle(); !eq(sp, test.sp) {
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t.Fatalf("%v.Saddle() = %v, want %v", m, sp, test.sp)
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}
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}
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}
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func eq(got, exp []Pair) bool {
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if len(got) != len(exp) {
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return false
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}
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exp:
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for _, e := range exp {
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for _, g := range got {
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if g == e {
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continue exp
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}
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}
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return false
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}
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return true
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}
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func BenchmarkSaddle(b *testing.B) {
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ms := make([]*Matrix, len(tests))
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var err error
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for i, test := range tests {
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if ms[i], err = New(test.m); err != nil {
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b.Fatalf("BenchmarkSaddle needs working New. "+
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"New(%s) returned %s. Error not expected.",
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test.m, err)
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}
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}
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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for _, m := range ms {
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m.Saddle()
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}
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}
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}
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