add new solutions

solutions/13/q1356/solution.go

@@ -0,0 +1,26 @@
+package q1356
+
+import "slices"
+
+func count1s(n int) int {
+	c := 0
+	for n > 0 {
+		c++
+		n = n & (n - 1)
+	}
+	return c
+}
+
+func sortByBits(arr []int) []int {
+	for i := range arr {
+		arr[i] += count1s(arr[i]) << 16
+	}
+	slices.Sort(arr)
+
+	for i := range arr {
+		arr[i] &= 1<<16 - 1
+	}
+	return arr
+}
+
+var _ = sortByBits