LeetCode Basic Calculator2

Description

Implement a basic calculator to evaluate a simple expression string.

The expression string contains only non-negative integers, +, -, *, / operators and empty spaces . The integer division should truncate toward zero.

You may assume that the given expression is always valid.

Some examples:
“3+2*2” = 7
“ 3/2 “ = 1
“ 3+5 / 2 “ = 5

The original problem is here.

The original code is here.

My Solution

I solve this problem in C++, as below:

/*
*Basic Calculator2
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<string.h>
#include<vector>
#include<stdlib.h>
using namespace std;

class Solution {
public:
    int calculate(string s) {
        if(s.length() <= 0)
            return 0;
        s.push_back(' ');
        vector<int>  myNumber;
        vector<char> myOperator;
        int num=0, sizeO=0, sizeN=0;
        bool isNum = false;
        for(int i=0;i<s.length();i++){
            cout<<"s["<<i<<"]="<<s[i]<<endl;
            if(s[i]>='0' && s[i]<='9'){
                num = num * 10 + (s[i]-'0');
                isNum = true;
            }
            else{
                if(isNum){
                    isNum = false;
                    sizeO = myOperator.size();
                    sizeN = myNumber.size();
                    if(sizeN == 0){
                        myNumber.push_back(num);
                    }
                    else{
                        cout<<"sizeO="<<sizeO<<endl<<"sizeN="<<sizeN<<endl;
                        if(myOperator[sizeO-1] =='*'){
                            myNumber[sizeN-1]  *=  num;
                            myOperator.pop_back();
                        }
                        else if(myOperator[sizeO-1]=='/'){
                            myNumber[sizeN-1]  /=  num;
                            myOperator.pop_back();
                        }
                        else{
                            myNumber.push_back(num);
                        }
                    }
                    num = 0;
                }
                if(s[i]=='+' || s[i]=='-' || s[i]=='*' || s[i]=='/'){
                    cout<<"!!s="<<s[i]<<endl;
                    myOperator.push_back(s[i]);
                }
                    
            }
        }
        if(myNumber.size()==0)
            return 0;
        if(myNumber.size()==1)
            return myNumber[0];
        int total = myNumber[0];
        for(int i=1;i<myNumber.size();i++){
            if(myOperator[i-1]=='+')
                total += myNumber[i];
            else if(myOperator[i-1]=='-')
                total -= myNumber[i];
        }
        return total;
    }
};
//the code under below is used for test
int main(){
    Solution s;
    string str("2*3+4") ;
    int num = s.calculate(str);
    cout<<"num="<<num<<endl;
    system("pause");
    return 0;
}

Note

We should note the priority of the operators: ‘+’, ‘-‘, ‘*’, ‘/‘.