diff --git a/problems/0216.组合总和III.md b/problems/0216.组合总和III.md
index 19fe1eb9..3b396b31 100644
--- a/problems/0216.组合总和III.md
+++ b/problems/0216.组合总和III.md
@@ -475,28 +475,36 @@ function combinationSum3(k: number, n: number): number[][] {
 
 ```Rust
 impl Solution {
-    fn backtracking(result: &mut Vec<Vec<i32>>, path:&mut Vec<i32>, targetSum:i32, k: i32, mut sum: i32, startIndex: i32) {
+    pub fn combination_sum3(k: i32, n: i32) -> Vec<Vec<i32>> {
+        let mut result = vec![];
+        let mut path = vec![];
+        Self::backtrace(&mut result, &mut path, n, k, 0, 1);
+        result
+    }
+    pub fn backtrace(
+        result: &mut Vec<Vec<i32>>,
+        path: &mut Vec<i32>,
+        target_sum: i32,
+        k: i32,
+        sum: i32,
+        start_index: i32,
+    ) {
+        if sum > target_sum {
+            return;
+        }
         let len = path.len() as i32;
         if len == k {
-            if sum == targetSum {
+            if sum == target_sum {
                 result.push(path.to_vec());
             }
             return;
         }
-        for i in startIndex..=9 {
-            sum += i;
+        for i in start_index..=9 - (k - len) + 1 {
             path.push(i);
-            Self::backtracking(result, path, targetSum, k, sum, i+1);
-            sum -= i;
+            Self::backtrace(result, path, target_sum, k, sum + i, i + 1);
             path.pop();
         }
     }
-    pub fn combination_sum3(k: i32, n: i32) -> Vec<Vec<i32>> {
-        let mut result: Vec<Vec<i32>> = Vec::new();
-        let mut path: Vec<i32> = Vec::new();
-        Self::backtracking(&mut result, &mut path, n, k, 0, 1);
-        result
-    }
 }
 ```