add solution of combination-sum

Author: jinhyungrhee

combination-sum/jinhyungrhee.java

@@ -0,0 +1,28 @@
+import java.util.*;
+class Solution {
+    public List<List<Integer>> output;
+    public List<List<Integer>> combinationSum(int[] candidates, int target) {
+        output = new ArrayList<>();
+        Deque<Integer> stack = new ArrayDeque<>();
+        dfs(candidates, target, stack, 0, 0);
+        return output;
+
+    }
+
+    public void dfs(int[] candidates, int target, Deque<Integer> stack, int start, int total) {
+
+        if (total > target) return;
+
+        if (total == target) {
+            output.add(new ArrayList<>(stack));
+            return;
+        }
+
+        for (int i = start; i < candidates.length; i++) {
+            int num = candidates[i];
+            stack.push(num);
+            dfs(candidates, target, stack, i, total + num);
+            stack.pop();
+        }
+    }
+}