update 0150.逆波兰表达式求值.md about rust

problems/0150.逆波兰表达式求值.md

@@ -89,12 +89,8 @@ C++代码如下：
 class Solution {
 public:
     int evalRPN(vector<string>& tokens) {
-<<<<<<< HEAD
-        stack<long long> st;
-=======
         // 力扣修改了后台测试数据，需要用longlong
         stack<long long> st; 
->>>>>>> 28f3b52a82e3cc650290fb02030a53900e122f43
         for (int i = 0; i < tokens.size(); i++) {
             if (tokens[i] == "+" || tokens[i] == "-" || tokens[i] == "*" || tokens[i] == "/") {
                 long long num1 = st.top();
@@ -424,6 +420,41 @@ object Solution {
 
 }
 ```
+
+rust:
+
+```rust
+impl Solution {
+    pub fn eval_rpn(tokens: Vec<String>) -> i32 {
+        let mut stack = vec![];
+        for token in tokens.into_iter() {
+            match token.as_str() {
+                "+" => {
+                    let a = stack.pop().unwrap();
+                    *stack.last_mut().unwrap() += a;
+                }
+                "-" => {
+                    let a = stack.pop().unwrap();
+                    *stack.last_mut().unwrap() -= a;
+                }
+                "*" => {
+                    let a = stack.pop().unwrap();
+                    *stack.last_mut().unwrap() *= a;
+                }
+                "/" => {
+                    let a = stack.pop().unwrap();
+                    *stack.last_mut().unwrap() /= a;
+                }
+                _ => {
+                    stack.push(token.parse::<i32>().unwrap());
+                }
+            }
+        }
+        stack.pop().unwrap()
+    }
+}
+```
+
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