Update 0070.爬楼梯.md

problems/0070.爬楼梯.md

@@ -454,19 +454,16 @@ public class Solution {
 ```rust
 impl Solution {
     pub fn climb_stairs(n: i32) -> i32 {
-        if n <= 2 {
+        if n <= 1 {
             return n;
         }
-        let mut a = 1;
-        let mut b = 2;
-        let mut f = 0;
-        for i in 2..n {
+        let (mut a, mut b, mut f) = (1, 1, 0);
+        for _ in 2..=n {
             f = a + b;
             a = b;
             b = f;
         }
-        return f;
-    }
+        f
 }
 ```