diff --git a/problems/0216.组合总和III.md b/problems/0216.组合总和III.md
index 2c1bf717..50c0d746 100644
--- a/problems/0216.组合总和III.md
+++ b/problems/0216.组合总和III.md
@@ -260,6 +260,37 @@ class Solution {
 		}
 	}
 }
+
+// 上面剪枝 i <= 9 - (k - path.size()) + 1; 如果还是不清楚
+// 也可以改为 if (path.size() > k) return; 执行效率上是一样的
+class Solution {
+    LinkedList<Integer> path = new LinkedList<>();
+    List<List<Integer>> ans = new ArrayList<>();
+    public List<List<Integer>> combinationSum3(int k, int n) {
+        build(k, n, 1, 0);
+        return ans;
+    }
+
+    private void build(int k, int n, int startIndex, int sum) {
+        
+        if (sum > n) return;
+
+        if (path.size() > k) return;
+
+        if (sum == n && path.size() == k) {
+            ans.add(new ArrayList<>(path));
+            return;
+        }
+        
+        for(int i = startIndex; i <= 9; i++) {
+            path.add(i);
+            sum += i;
+            build(k, n, i + 1, sum);
+            sum -= i;
+            path.removeLast();
+        }
+    }
+}
 ```
 
 其他方法