0216. Combination Sum III V1.0

Author: ChlZhYa

LeetCode/0216. Combination Sum III/src/Solution.java

@@ -0,0 +1,31 @@
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.LinkedList;
+import java.util.List;
+
+/**
+ * @author changleamazing
+ * @date 2020/9/12 21:13
+ **/
+public class Solution {
+    public List<List<Integer>> combinationSum3(int k, int n) {
+        List<List<Integer>> res = new ArrayList<>();
+        Deque<Integer> queue = new LinkedList<>();
+        backtrace(1, k, n, queue, res);
+        return res;
+    }
+
+    private void backtrace(int number, int restCount, int restSum, Deque<Integer> queue, List<List<Integer>> res) {
+        if (restCount == 0) {
+            if (restSum == 0) {
+                res.add(new ArrayList<>(queue));
+            }
+            return;
+        }
+        for (int i = number; i <= restSum && i <= 9; i++) {
+            queue.add(i);
+            backtrace(i + 1, restCount - 1, restSum - i, queue, res);
+            queue.removeLast();
+        }
+    }
+}