Update 0746.使用最小花费爬楼梯.md

problems/0746.使用最小花费爬楼梯.md

@@ -351,17 +351,29 @@ function minCostClimbingStairs(cost: number[]): number {
 ### Rust
 
 ```Rust
-use std::cmp::min;
 impl Solution {
     pub fn min_cost_climbing_stairs(cost: Vec<i32>) -> i32 {
-        let len = cost.len();
-        let mut dp = vec![0; len];
-        dp[0] = cost[0];
-        dp[1] = cost[1];
-        for i in 2..len {
-            dp[i] = min(dp[i-1], dp[i-2]) + cost[i];
+        let mut dp = vec![0; cost.len() + 1];
+        for i in 2..=cost.len() {
+            dp[i] = (dp[i - 1] + cost[i - 1]).min(dp[i - 2] + cost[i - 2]);
         }
-        min(dp[len-1], dp[len-2])
+        dp[cost.len()]
+    }
+}
+```
+
+不使用 dp 数组
+
+```rust
+impl Solution {
+    pub fn min_cost_climbing_stairs(cost: Vec<i32>) -> i32 {
+        let (mut dp_before, mut dp_after) = (0, 0);
+        for i in 2..=cost.len() {
+            let dpi = (dp_before + cost[i - 2]).min(dp_after + cost[i - 1]);
+            dp_before = dp_after;
+            dp_after = dpi;
+        }
+        dp_after
     }
 }
 ```