Merge pull request youngyangyang04#2103 from fwqaaq/patch-24

Update 0518.零钱兑换II.md 优化 Rust

problems/0518.零钱兑换II.md

@@ -282,17 +282,18 @@ func change(amount int, coins []int) int {
 
 Rust:
 ```rust
-pub fn change(amount: i32, coins: Vec<i32>) -> i32 {
-    let amount = amount as usize;
-    let coins = coins.iter().map(|&c|c as usize).collect::<Vec<usize>>();
-    let mut dp = vec![0usize; amount + 1];
-    dp[0] = 1;
-    for i in 0..coins.len() {
-        for j in coins[i]..=amount {
-            dp[j] += dp[j - coins[i]];
+impl Solution {
+    pub fn change(amount: i32, coins: Vec<i32>) -> i32 {
+        let amount = amount as usize;
+        let mut dp = vec![0; amount + 1];
+        dp[0] = 1;
+        for coin in coins {
+            for j in coin as usize..=amount {
+                dp[j] += dp[j - coin as usize];
+            }
         }
+        dp[amount]
     }
-    dp[amount] as i32
 }
 ```