0039. Combination Sum V1.0

Author: ChlZhYa

LeetCode/0039. Combination Sum/src/Solution.java

@@ -0,0 +1,38 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Deque;
+import java.util.LinkedList;
+import java.util.List;
+
+/**
+ * @author changleamazing
+ * @date 2020/9/11 16:36 source: https://leetcode-cn.com/problems/combination-sum/
+ **/
+public class Solution {
+
+    public List<List<Integer>> combinationSum(int[] candidates, int target) {
+        if(candidates.length == 0){
+            return null;
+        }
+        Arrays.sort(candidates);
+        List<List<Integer>> res = new ArrayList<>();
+        Deque<Integer> tempList = new LinkedList<>();
+        backtrace(candidates,0,target,tempList,res);
+        return res;
+    }
+
+    private void backtrace(int[] candidates,int begin,int target,Deque<Integer> tempQueue,List<List<Integer>> res){
+        if(target == 0){
+            res.add(new ArrayList<>(tempQueue));
+            return;
+        }
+        for(int i = begin;i < candidates.length ;i++){
+            if(target < candidates[i]){
+                break;
+            }
+            tempQueue.add(candidates[i]);
+            backtrace(candidates, i, target - candidates[i], tempQueue, res);
+            tempQueue.removeLast();
+        }
+    }
+}