Update 回溯算法去重问题的另一种写法.md

problems/回溯算法去重问题的另一种写法.md

@@ -561,6 +561,49 @@ impl Solution {
 }
 ```
 
+**40. 组合总和 II**
+
+```rust
+use std::collections::HashSet;
+impl Solution {
+    pub fn backtracking(
+        candidates: &Vec<i32>,
+        target: i32,
+        sum: i32,
+        path: &mut Vec<i32>,
+        res: &mut Vec<Vec<i32>>,
+        start_index: usize,
+    ) {
+        if sum > target {
+            return;
+        }
+        if sum == target {
+            res.push(path.clone());
+        }
+        let mut helper_set = HashSet::new();
+        for i in start_index..candidates.len() {
+            if sum + candidates[i] <= target {
+                if helper_set.contains(&candidates[i]) {
+                    continue;
+                }
+                helper_set.insert(candidates[i]);
+                path.push(candidates[i]);
+                Self::backtracking(candidates, target, sum + candidates[i], path, res, i + 1);
+                path.pop();
+            }
+        }
+    }
+
+    pub fn combination_sum2(mut candidates: Vec<i32>, target: i32) -> Vec<Vec<i32>> {
+        let mut res = vec![];
+        let mut path = vec![];
+        candidates.sort();
+        Self::backtracking(&candidates, target, 0, &mut path, &mut res, 0);
+        res
+    }
+}
+```
+
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