solved: 31

Author: ryoppippi

code/31.next-permutation.ts

@@ -0,0 +1,29 @@
+// @leet start
+/**
+ * swap the first number that is smaller than the number after it
+ */
+function nextPermutation(nums: number[]): void {
+  let i = nums.length - 2;
+  while (i >= 0 && nums[i] >= nums[i + 1]) {
+    i--;
+  }
+
+  if (i >= 0) {
+    let j = nums.length - 1;
+    while (j >= 0 && nums[j] <= nums[i]) {
+      j--;
+    }
+
+    [nums[i], nums[j]] = [nums[j], nums[i]];
+  }
+
+  // reverse the rest
+
+  const s = nums.slice(i + 1);
+  s.reverse();
+  s.forEach((v, index) => {
+    nums[i + 1 + index] = v;
+  });
+}
+// @leet end
+