Redo 39

Author: ChienkuChen

src/_39/39.combination-sum.java

@@ -1,39 +1,41 @@
 package _39;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 
 class Solution {
     public List<List<Integer>> combinationSum(int[] candidates, int target) {
-        Arrays.sort(candidates);
-        return find(candidates, target, 0);
+        if (candidates == null || candidates.length == 0)
+            return new ArrayList<>();
+
+        List<List<Integer>> result = new ArrayList<>();
+
+        helper(candidates, target, 0, new ArrayList<>(), result);
+
+        return result;
     }
 
-    public List<List<Integer>> find(int[] candidates, int target, int start) {
-        if (target <= 0)
-            return new ArrayList<>();
+    private void helper(int[] candidates, int target, int start, List<Integer> tmp, List<List<Integer>> result) {
+        if (target < 0)
+            return;
 
-        List<List<Integer>> results = new ArrayList<>();
-        for (int i = start; i < candidates.length; i++) {
-            if (target - candidates[i] == 0) {
-                List<Integer> list = new ArrayList<>();
-                list.add(candidates[i]);
-                results.add(list);
-                return results;
-            }
-
-            List<List<Integer>> lists = find(candidates, target - candidates[i], i);
-            for (List<Integer> list : lists) {
-                list.add(candidates[i]);
-                results.add(list);
-            }
+        if (target == 0) {
+            result.add(tmp);
+            return;
         }
 
-        return results;
+        if (start >= candidates.length)
+            return;
+
+        helper(candidates, target, start + 1, tmp, result);
+
+        List<Integer> list = new ArrayList<>(tmp);
+        list.add(candidates[start]);
+        helper(candidates, target - candidates[start], start, list, result);
     }
 
     public static void main(String[] args) {
+        System.out.println(new Solution().combinationSum(new int[]{2, 3, 5}, 8));
         System.out.println(new Solution().combinationSum(new int[]{2, 3, 6, 7}, 7));
     }
-}
+}

src/_39/39.combination-sum.java.bak

@@ -0,0 +1,39 @@
+package _39;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+class Solution {
+    public List<List<Integer>> combinationSum(int[] candidates, int target) {
+        Arrays.sort(candidates);
+        return find(candidates, target, 0);
+    }
+
+    public List<List<Integer>> find(int[] candidates, int target, int start) {
+        if (target <= 0)
+            return new ArrayList<>();
+
+        List<List<Integer>> results = new ArrayList<>();
+        for (int i = start; i < candidates.length; i++) {
+            if (target - candidates[i] == 0) {
+                List<Integer> list = new ArrayList<>();
+                list.add(candidates[i]);
+                results.add(list);
+                return results;
+            }
+
+            List<List<Integer>> lists = find(candidates, target - candidates[i], i);
+            for (List<Integer> list : lists) {
+                list.add(candidates[i]);
+                results.add(list);
+            }
+        }
+
+        return results;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(new Solution().combinationSum(new int[]{2, 3, 6, 7}, 7));
+    }
+}