Remove string operations

2018/day05/day05.go

@@ -2,26 +2,26 @@ package main
 
 import (
 	"bufio"
+	"bytes"
 	"fmt"
 	"log"
 	"math"
 	"os"
 	"strconv"
-	"strings"
 )
 
 func main() {
-	inp := StdinToString()
+	inp := []byte(StdinToString())
 	fmt.Println("= Part 1 =")
 	fmt.Println(part1(inp))
 	fmt.Println("\n= Part 2 =")
 	fmt.Println(part2(inp))
 }
 
-func part1(inp string) int {
+func part1(inp []byte) int {
 	last := inp
 	curr := react(last)
-	for last != curr {
+	for !bytes.Equal(last, curr) {
 		last = curr
 		curr = react(last)
 	}
@@ -32,16 +32,16 @@ func part1(inp string) int {
 // It reduced _my_ runtime by about 3 minutes, but may fail depending on your input
 var useShortest bool
 
-func part2(inp string) int {
+func part2(inp []byte) int {
 	// If yours fails, try setting this to false
 	useShortest = true
 	shortest := len(inp)
 	var shortestCount int
 	var count int
 	for i := 65; i <= 90; i++ {
-		var try string
+		var try []byte
 		if useShortest {
-			count = strings.Count(inp, string(i))
+			count = countByte(inp, byte(i))
 			if count < shortestCount {
 				continue
 			}
@@ -50,7 +50,7 @@ func part2(inp string) int {
 			if int(inp[j]) == i || int(inp[j]) == i+32 {
 				continue
 			}
-			try += string(inp[j])
+			try = append(try, inp[j])
 		}
 		v := part1(try)
 		if v < shortest {
@@ -61,14 +61,24 @@ func part2(inp string) int {
 	return shortest
 }
 
-func react(v string) string {
-	var ret string
+func countByte(h []byte, n byte) int {
+	var ret int
+	for i := range h {
+		if h[i] == n {
+			ret++
+		}
+	}
+	return ret
+}
+
+func react(v []byte) []byte {
+	var ret []byte
 	for i := 0; i < len(v); i++ {
 		if i < len(v)-1 && Abs(v[i], v[i+1]) == 32 {
 			i++
 			continue
 		}
-		ret += string(v[i])
+		ret = append(ret, v[i])
 	}
 	return ret
 }