Passed only small judge.

Author: yuduozhou

CombinationSum.java

@@ -0,0 +1,29 @@
+public class Solution {
+    public ArrayList<ArrayList<Integer>> combinationSum(int[] candidates, int target) {
+        // Start typing your Java solution below
+        // DO NOT write main() function
+        ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
+        Stack<Integer> stack = new Stack<Integer>();
+        Arrays.sort(candidates);
+        combinationHelper(candidates, stack, result, target);
+        return result;
+    }
+    
+    public void combinationHelper(int[] candidates, Stack<Integer> stack, ArrayList<ArrayList<Integer>> result, int target){
+        if (target <= 0){
+            if (target == 0){
+                ArrayList<Integer> temp = new ArrayList<Integer>(stack);
+                Collections.sort(temp);
+                if (!result.contains(temp)){
+                    result.add(temp);
+                }
+            }
+            return;
+        }
+        for (int i = 0; i < candidates.length; i ++){
+            stack.push(candidates[i]);
+            combinationHelper(candidates, stack, result, target - candidates[i]);
+            stack.pop();
+        }
+    }
+}

CombinationSum2.java

@@ -0,0 +1,31 @@
+public class Solution {
+    public ArrayList<ArrayList<Integer>> combinationSum2(int[] candidates, int target) {
+        // Start typing your Java solution below
+        // DO NOT write main() function
+        ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
+        Stack<Integer> stack = new Stack<Integer>();
+        Arrays.sort(candidates);
+        combinationHelper(candidates, stack, result, target, 0);
+        return result;
+    }
+    
+    public void combinationHelper(int[] candidates, Stack<Integer> stack, ArrayList<ArrayList<Integer>> result, int target, int start){
+        if (target <= 0){
+            if (target == 0){
+                ArrayList<Integer> temp = new ArrayList<Integer>(stack);
+                Collections.sort(temp);
+                if (!result.contains(temp)){
+                    result.add(temp);
+                }
+            }
+            return;
+        }
+        if (start == candidates.length) return;
+        for (int i = start; i < candidates.length; i ++){
+            stack.push(candidates[i]);
+            combinationHelper(candidates, stack, result, target - candidates[i], ++start);
+            stack.pop();
+        }
+
+    }
+}