leetcode: Add 0150

src/leetcode/0150.evaluate-reverse-polish-notation/Cargo.toml

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+[package]
+name = "lc-0150-evaluate-reverse-polish-notation"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]

src/leetcode/0150.evaluate-reverse-polish-notation/index.md

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+
+# 
+
+[问题描述](../problems/)

src/leetcode/0150.evaluate-reverse-polish-notation/src/main.rs

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+// Copyright (c) 2024 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+// Stack
+// 后缀表达式
+pub fn eval_rpn1(tokens: Vec<String>) -> i32 {
+    let mut stack: Vec<i32> = Vec::new();
+
+    for token in tokens.iter() {
+        match token.as_str() {
+            // 匹配运算符.
+            op @ ("+" | "-" | "*" | "/") => {
+                assert!(stack.len() >= 2);
+                // 要注意栈中两个整数的顺序.
+                let num1 = stack.pop().unwrap();
+                let num2 = stack.pop().unwrap();
+                let res = match op {
+                    "+" => num2 + num1,
+                    "-" => num2 - num1,
+                    "*" => num2 * num1,
+                    "/" => num2 / num1,
+                    // unreachable!()
+                    _ => 0,
+                };
+                // 将计算结果入栈.
+                stack.push(res);
+            }
+            num_str => {
+                //let num: i32 = i32::from_str(num_str).unwrap();
+                //let num: i32 = i32::from_str_radix(num_str, 10).unwrap();
+                let num: i32 = num_str.parse().unwrap();
+                stack.push(num);
+            }
+        }
+    }
+    // 栈顶的元素就是计算结果.
+    stack.pop().unwrap()
+}
+
+// Stack
+// 后缀表达式
+// - 优化模式匹配
+// - 优化出栈操作
+pub fn eval_rpn2(tokens: Vec<String>) -> i32 {
+    let mut stack: Vec<i32> = Vec::with_capacity(tokens.len());
+
+    for token in tokens.iter() {
+        match token.as_str() {
+            // 匹配运算符.
+            "+" => {
+                debug_assert!(stack.len() >= 2);
+                let num1 = stack.pop().unwrap();
+                let num2 = stack.last_mut().unwrap();
+                *num2 += num1;
+            }
+            "-" => {
+                debug_assert!(stack.len() >= 2);
+                let num1 = stack.pop().unwrap();
+                let num2 = stack.last_mut().unwrap();
+                *num2 -= num1;
+            }
+            "*" => {
+                debug_assert!(stack.len() >= 2);
+                let num1 = stack.pop().unwrap();
+                let num2 = stack.last_mut().unwrap();
+                *num2 *= num1;
+            }
+            "/" => {
+                debug_assert!(stack.len() >= 2);
+                let num1 = stack.pop().unwrap();
+                let num2 = stack.last_mut().unwrap();
+                *num2 /= num1;
+            }
+            num_str => {
+                //let num: i32 = i32::from_str(num_str).unwrap();
+                //let num: i32 = i32::from_str_radix(num_str, 10).unwrap();
+                let num: i32 = num_str.parse().unwrap();
+                stack.push(num);
+            }
+        }
+    }
+    // 栈顶的元素就是计算结果.
+    stack.pop().unwrap()
+}
+
+pub type SolutionFn = fn(Vec<String>) -> i32;
+
+fn check_solution(func: SolutionFn) {
+    const RECORDS: &[(&[&str], i32)] = &[
+        (&["2", "1", "+", "3", "*"], 9),
+        (&["4", "13", "5", "/", "+"], 6),
+        (
+            &[
+                "10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+",
+            ],
+            22,
+        ),
+    ];
+
+    for record in RECORDS {
+        let token: Vec<String> = record.0.iter().map(|val| val.to_string()).collect();
+        let output = record.1;
+        assert_eq!(func(token), output);
+    }
+}
+
+fn main() {
+    check_solution(eval_rpn1);
+    check_solution(eval_rpn2);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{check_solution, eval_rpn1, eval_rpn2};
+
+    #[test]
+    fn test_eval_rpn1() {
+        check_solution(eval_rpn1);
+    }
+
+    #[test]
+    fn test_eval_rpn2() {
+        check_solution(eval_rpn2);
+    }
+}