AB6 表达式求值

class Solution { public: vector function(string s, int index){ stack stack; int num = 0; char op = '+'; int i; for(i = index; i < s.length(); i++){ //数字转换成int数字 if(isdigit(s[i])){ num = num * 10 + s[i] - '0'; if(i != s.length() - 1) continue; } //碰到'('时，把整个括号内的当成一个数字处理 if(s[i] == '('){ //递归处理括号 vector res = function(s, i + 1); num = res[0]; i = res[1]; if(i != s.length() - 1) continue; }
switch(op){ //加减号先入栈 case '+': stack.push(num); break; case '-': //相反数 stack.push(-num); break; //优先计算乘号 case '*':
int temp = stack.top(); stack.pop(); stack.push(temp * num); break; } num = 0; //右括号结束递归 if(s[i] == ')') break; else op = s[i]; } int sum = 0; //栈中元素相加 while(!stack.empty()){
sum += stack.top(); stack.pop(); } return vector {sum, i}; }

int solve(string s) {
    return function(s, 0)[0];
}

};