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Author: assassint2017

Combination Sum III/Combination_Sum_III.cpp

@@ -0,0 +1,58 @@
+class Solution
+{
+public:
+	vector<vector<int>> combinationSum3(int k, int n)
+	{
+		vector<vector<int>> res;
+		vector<int> candidate;
+
+		dfs(res, candidate, k, n, 1);
+
+		return res;
+	}
+private:
+	void dfs(vector<vector<int>>& res, vector<int>& candidate, int n, int target, int start)
+	{
+		if (n == 2)
+		{
+			int leftPtr = start;
+			int rightPtr = 9;
+
+			while (leftPtr < rightPtr)
+			{
+				if (leftPtr + rightPtr == target)
+				{
+					candidate.push_back(leftPtr);
+					candidate.push_back(rightPtr);
+
+					res.push_back(candidate);
+
+					candidate.pop_back();
+					candidate.pop_back();
+
+					++leftPtr;
+					--rightPtr;
+				}
+				else if (leftPtr + rightPtr > target)
+				{
+					--rightPtr;
+				}
+				else
+				{
+					++leftPtr;
+				}
+			}
+		}
+		else
+		{
+			for (int i = start; i <= 9; ++i)
+			{
+				candidate.push_back(i);
+
+				dfs(res, candidate, n - 1, target - i, i + 1);
+
+				candidate.pop_back();
+			}
+		}
+	}
+};