fix: check the rust codes and fix them (#653)

* fix: check the rust codes and fix it

* Update binary_tree_bfs.rs

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Co-authored-by: Yudong Jin <krahets@163.com>

codes/rust/chapter_backtracking/subset_sum_i_naive.rs

@@ -29,8 +29,8 @@ fn backtrack(mut state: Vec<i32>, target: i32, total: i32, choices: &[i32], res:
 /* 求解子集和 I（包含重复子集） */
 fn subset_sum_i_naive(nums: &[i32], target: i32) -> Vec<Vec<i32>> {
     let state = Vec::new(); // 状态（子集）
-    let total = 0;
-    let mut res = Vec::new();
+    let total = 0; // 子集和
+    let mut res = Vec::new(); // 结果列表（子集列表）
     backtrack(state, target, total, nums, &mut res);
     res
 }