Create Next Permutation algo

Next Permutation algo

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+
+class Solution {
+public:
+    void nextPermutation(vector<int> &num) 
+    {
+        if (num.empty()) return;
+
+        // in reverse order, find the first number which is in increasing trend (we call it violated number here)
+        int i;
+        for (i = num.size()-2; i >= 0; --i)
+        {
+            if (num[i] < num[i+1]) break;
+        }
+
+        // reverse all the numbers after violated number
+        reverse(begin(num)+i+1, end(num));
+        // if violated number not found, because we have reversed the whole array, then we are done!
+        if (i == -1) return;
+        // else binary search find the first number larger than the violated number
+        auto itr = upper_bound(begin(num)+i+1, end(num), num[i]);
+        // swap them, done!
+        swap(num[i], *itr);
+    }
+};