A: Increasing Decreasing String

Author: Shuo

problems/increasing-decreasing-string/increasing_decreasing_string.go

@@ -0,0 +1,26 @@
+package problem1370
+
+func sortString(s string) string {
+	var m [26]int
+	for _, c := range s {
+		m[c-'a']++
+	}
+	l := len(s)
+	ans := make([]byte, 0, l)
+	appendChar := func(c int) {
+		if m[c] > 0 {
+			m[c]--
+			l--
+			ans = append(ans, byte(c+'a'))
+		}
+	}
+	for l > 0 {
+		for i := 0; i <= 25; i++ {
+			appendChar(i)
+		}
+		for i := 25; i >= 0; i-- {
+			appendChar(i)
+		}
+	}
+	return string(ans)
+}

problems/increasing-decreasing-string/increasing_decreasing_string_test.go

@@ -0,0 +1,39 @@
+package problem1370
+
+import "testing"
+
+type testType struct {
+	in   string
+	want string
+}
+
+func TestSortString(t *testing.T) {
+	tests := [...]testType{
+		{
+			in:   "aaaabbbbcccc",
+			want: "abccbaabccba",
+		},
+		{
+			in:   "rat",
+			want: "art",
+		},
+		{
+			in:   "leetcode",
+			want: "cdelotee",
+		},
+		{
+			in:   "ggggggg",
+			want: "ggggggg",
+		},
+		{
+			in:   "spo",
+			want: "ops",
+		},
+	}
+	for _, tt := range tests {
+		got := sortString(tt.in)
+		if got != tt.want {
+			t.Fatalf("in: %v, got: %v, want: %v", tt.in, got, tt.want)
+		}
+	}
+}