Merge pull request #2161 from fwqaaq/patch-44

Update 0714.买卖股票的最佳时机含手续费（动态规划）.md 优化 Rust

problems/0714.买卖股票的最佳时机含手续费（动态规划）.md

@@ -270,18 +270,29 @@ impl Solution {
 **动态规划**
 ```Rust
 impl Solution {
-    fn max(a: i32, b: i32) -> i32 {
-        if a > b { a } else { b }
-    }
     pub fn max_profit(prices: Vec<i32>, fee: i32) -> i32 {
-        let n = prices.len();
-        let mut dp = vec![vec![0; 2]; n];
-        dp[0][0] -= prices[0];
-        for i in 1..n {
-            dp[i][0] = Self::max(dp[i - 1][0], dp[i - 1][1] - prices[i]);
-            dp[i][1] = Self::max(dp[i - 1][1], dp[i - 1][0] + prices[i] - fee);
+        let mut dp = vec![vec![0; 2]; prices.len()];
+        dp[0][0] = -prices[0];
+        for (i, &p) in prices.iter().enumerate().skip(1) {
+            dp[i][0] = dp[i - 1][0].max(dp[i - 1][1] - p);
+            dp[i][1] = dp[i - 1][1].max(dp[i - 1][0] + p - fee);
         }
-        Self::max(dp[n - 1][0], dp[n - 1][1])
+        dp[prices.len() - 1][1]
+    }
+}
+```
+
+**动态规划空间优化**
+
+```rust
+impl Solution {
+    pub fn max_profit(prices: Vec<i32>, fee: i32) -> i32 {
+        let (mut low, mut res) = (-prices[0], 0);
+        for p in prices {
+            low = low.max(res - p);
+            res = res.max(p + low - fee);
+        }
+        res
     }
 }
 ```