Update and rename nextPermutation.cpp to next-permutation.cpp

Author: kamyu104

C++/next-permutation.cpp

@@ -0,0 +1,40 @@
+// Time:  O(n)
+// Space: O(1)
+
+class Solution {
+public:
+    void nextPermutation(vector<int> &num) {
+        nextPermutation(num.begin(), num.end());
+    }
+    
+private:
+    template<typename BidiIt>
+    bool nextPermutation(BidiIt begin, BidiIt end) {
+        const auto rbegin = reverse_iterator<BidiIt>(end);
+        const auto rend = reverse_iterator<BidiIt>(begin);
+        
+        // Find the first element (pivot) which is less than its successor.
+        auto pivot = next(rbegin);
+        while (pivot != rend && *pivot >= *prev(pivot)) {
+            ++pivot;
+        }
+        
+        if (pivot != rend) {
+            // Find the number which is greater than pivot, and swap it with pivot
+            auto change = find_if(rbegin, pivot, bind1st(less<int>(), *pivot));
+            swap(*change, *pivot);
+        }
+        
+        // Make the sequence after pivot non-descending
+        reverse(rbegin, pivot);
+        
+        return true;
+    }
+};
+
+class Solution2 {
+public:
+    void nextPermutation(vector<int> &num) {
+        next_permutation(num.begin(), num.end());
+    }
+};