Update next-permutation.cpp

Author: kamyu104

C++/next-permutation.cpp

@@ -2,6 +2,30 @@
 // Space: O(1)
 
 class Solution {
+public:
+    void nextPermutation(vector<int>& nums) {
+        int pivot = -1;
+        for (int i = nums.size() - 2; i >= 0; --i) {
+            if (nums[i] < nums[i + 1]) {
+                pivot = i;
+                break;
+            }
+        }
+        if (pivot == -1) {
+            reverse(begin(nums), end(nums));
+            return;
+        }
+        for (int i = nums.size() - 1; i > pivot; --i) {
+            if (nums[i] > nums[pivot]) {
+                swap(nums[pivot], nums[i]);
+                break;
+            }
+        }
+        reverse(begin(nums) + pivot + 1, end(nums));
+    }
+};
+
+class Solution2 {
 public:
     void nextPermutation(vector<int> &num) {
         nextPermutation(num.begin(), num.end());
@@ -35,7 +59,7 @@ class Solution {
     }
 };
 
-class Solution2 {
+class Solution3 {
 public:
     void nextPermutation(vector<int> &num) {
         next_permutation(num.begin(), num.end());