题解 | #逆波兰表达式求值#
逆波兰表达式求值
https://www.nowcoder.com/practice/885c1db3e39040cbae5cdf59fb0e9382
使用栈求解很方便得到：
import java.util.*;
public class Solution {
/**
* 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
*
*
* @param tokens string字符串一维数组
* @return int整型
*/
public int evalRPN (String[] tokens) {
// write code here
int tmp=0;
Stack<Integer> stack=new Stack<>();
int n = tokens.length;
int x;
for(int i=0;i<n;i++){
switch(tokens[i]){
case "+":
tmp = stack.pop()+stack.pop();
stack.push(tmp);
break;
case "-":
x=stack.pop();
tmp = stack.pop()-x;
stack.push(tmp);
break;
case "*":
tmp = stack.pop()*stack.pop();
stack.push(tmp);
break;
case "/":
x=stack.pop();
tmp = stack.pop()/x;
stack.push(tmp);
break;
default:
stack.push(Integer.parseInt(tokens[i]));
}
}
return stack.pop();
}
}
