1

Author: kedebug

Combinations/Combinations.cpp

@@ -0,0 +1,27 @@
+class Solution {
+public:
+    vector<vector<int> > combine(int n, int k) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        vector<vector<int>> result;
+        vector<int> comb;
+        DFS(comb, 0, 0, k, n, result);
+        return move(result);
+    }
+    
+    void DFS(vector<int>& comb, int step, int p, int k, int n, vector<vector<int>>& result) {
+        if (step == k) {
+            result.push_back(comb);
+            return;
+        }
+        if (n - p < k - step) 
+            return;
+        
+        comb.push_back(p + 1);
+        DFS(comb, step + 1, p + 1, k, n, result);
+        comb.pop_back();
+        
+        DFS(comb, step, p + 1, k, n, result);
+    }
+};