add sol

leetcode/451.SortCharactersByFrequency/sortCharactersByFrequency.go

@@ -0,0 +1,57 @@
+// https://leetcode.com/problems/sort-characters-by-frequency
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+)
+
+func frequencySort(s string) string {
+
+	// count character
+	cnt := map[byte]int{}
+	for i := range s {
+		cnt[s[i]]++
+	}
+
+	// sort character
+	cs := make([]byte, 0, len(s))
+	for c := range cnt {
+		cs = append(cs, c)
+		fmt.Println(cs)
+	}
+	sort.Slice(cs, func(i, j int) bool { return cnt[cs[i]] > cnt[cs[j]] })
+	fmt.Println(cs)
+
+	for _, s := range cs {
+		tmp := sortString(string(s))
+		fmt.Println(tmp)
+	}
+
+	// append to res
+	res := make([]byte, 0, len(s))
+	for _, c := range cs {
+		res = append(res, bytes.Repeat([]byte{c}, cnt[c])...)
+	}
+	return string(res)
+}
+
+func sortString(s string) string {
+	bytes := []byte(s)
+	tmp := make([]int, len(bytes))
+	for i, b := range bytes {
+		tmp[i] = int(b)
+	}
+	sort.Ints(tmp)
+	for i, v := range tmp {
+		bytes[i] = byte(v)
+	}
+	return string(bytes)
+}
+
+func main() {
+	s := "aaabccc"
+	fmt.Println(frequencySort(s))
+}