T3:牛牛与后缀表达式

T3:牛牛与后缀表达式

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
     * 给定一个后缀表达式，返回它的结果
     * @param str string字符串 
     * @return long长整型
     */
    public long solve (String s) {
        int n = s.length();
        Stack<Long> stack = new Stack<>();
        long value = 0;
        long c=0;
        for(int i=0;i<n;i++){

            if(s.charAt(i) == '+'){
                long h = stack.pop();
                long q = stack.pop();
                stack.push(h+q);
            }else if(s.charAt(i) == '-'){
                long h = stack.pop();
                long q = stack.pop();
                stack.push(q-h);
            }else if(s.charAt(i) == '*'){
                long h = stack.pop();
                long q = stack.pop();
                stack.push(q*h);
            }else if(s.charAt(i) == '/'){
                long h = stack.pop();
                long q = stack.pop();
                stack.push(q/h);
            }else if(s.charAt(i) == '#'){
                stack.push(c);
                c=0;
            }else{
                c=c*10+(s.charAt(i)-'0');
            }
        }
        return stack.pop();
    }
}