Initial Commit

go/pascals-triangle/README.md

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+# Pascals Triangle
+
+Write a program that computes Pascal's triangle up to a given number of rows.
+
+In Pascal's Triangle each number is computed by adding the numbers to
+the right and left of the current position in the previous row.
+
+```plain
+    1
+   1 1
+  1 2 1
+ 1 3 3 1
+1 4 6 4 1
+# ... etc
+```
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://help.exercism.io/getting-started-with-go.html).
+
+## Source
+
+Pascal's Triangle at Wolfram Math World [view source](http://mathworld.wolfram.com/PascalsTriangle.html)

go/pascals-triangle/pascal.go

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+package pascal
+
+// Triangle returns pascals triangle up to depth
+func Triangle(depth int) [][]int {
+	var ret [][]int
+	for currDepth := 0; currDepth < depth; currDepth++ {
+		var newRow, prevRow []int
+		// Each row is currDepth+1 long
+		rowLength := currDepth + 1
+		// Rows start with a 1
+		newRow = append(newRow, 1)
+		if currDepth > 0 {
+			prevRow = ret[currDepth-1]
+		}
+		for i := 1; i < rowLength; i++ {
+			if i == rowLength-1 {
+				// Rows end with a 1 also
+				newRow = append(newRow, 1)
+				break
+			}
+			newRow = append(newRow, prevRow[i-1]+prevRow[i])
+		}
+		ret = append(ret, newRow)
+	}
+	return ret
+}

go/pascals-triangle/pascal_printer.go

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+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+
+	"gogs.bullercodeworks.com/brian/pascal"
+)
+
+func main() {
+	if len(os.Args) == 2 {
+		if num, err := strconv.Atoi(os.Args[1]); err == nil {
+			ret := pascal.Triangle(num)
+			for i := range ret {
+				fmt.Println(ret[i])
+			}
+			return
+		}
+	}
+	fmt.Println("Usage: ./pascal_printer <depth>")
+}

go/pascals-triangle/pascals_triangle_test.go

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+package pascal
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+)
+
+var t20 = [][]int{
+	{1},
+	{1, 1},
+	{1, 2, 1},
+	{1, 3, 3, 1},
+	{1, 4, 6, 4, 1},
+	{1, 5, 10, 10, 5, 1},
+	{1, 6, 15, 20, 15, 6, 1},
+	{1, 7, 21, 35, 35, 21, 7, 1},
+	{1, 8, 28, 56, 70, 56, 28, 8, 1},
+	{1, 9, 36, 84, 126, 126, 84, 36, 9, 1},
+	{1, 10, 45, 120, 210, 252, 210, 120, 45, 10, 1},
+	{1, 11, 55, 165, 330, 462, 462, 330, 165, 55, 11, 1},
+	{1, 12, 66, 220, 495, 792, 924, 792, 495, 220, 66, 12, 1},
+	{1, 13, 78, 286, 715, 1287, 1716, 1716, 1287, 715, 286, 78, 13, 1},
+	{1, 14, 91, 364, 1001, 2002, 3003, 3432, 3003, 2002, 1001, 364, 91, 14, 1},
+	{1, 15, 105, 455, 1365, 3003, 5005, 6435, 6435, 5005, 3003, 1365, 455, 105, 15, 1},
+	{1, 16, 120, 560, 1820, 4368, 8008, 11440, 12870, 11440, 8008, 4368, 1820, 560, 120, 16, 1},
+	{1, 17, 136, 680, 2380, 6188, 12376, 19448, 24310, 24310, 19448, 12376, 6188, 2380, 680, 136, 17, 1},
+	{1, 18, 153, 816, 3060, 8568, 18564, 31824, 43758, 48620, 43758, 31824, 18564, 8568, 3060, 816, 153, 18, 1},
+	{1, 19, 171, 969, 3876, 11628, 27132, 50388, 75582, 92378, 92378, 75582, 50388, 27132, 11628, 3876, 969, 171, 19, 1},
+}
+
+func TestTriangle(t *testing.T) {
+	for n := 1; n <= 20; n++ {
+		res := Triangle(n)
+		want := t20[:n]
+		if !reflect.DeepEqual(res, want) {
+			t.Fatalf("Triangle(%d) = %s,\nwant:%s\n",
+				n, format(res), format(want))
+		}
+	}
+	t.Log(format(Triangle(20)))
+}
+
+func format(t [][]int) (s string) {
+	for _, r := range t {
+		s = fmt.Sprintf("%s\n%v", s, r)
+	}
+	return
+}