[每日一题] leetcode 640. 求解方程

等号左右两边代码一样，就是+ - 不一样

将x都移到左边 整数移到右边

class Solution {
public:

    int change(string str)
    {
        if(str == "0") return 1;
        int len = str.length();
        int ret = 0;
        for(int i = 0; i < len; i++)
        {
            ret = ret * 10 + str[i] - '0';
        }
        return ret;
    }
    string rev(int x)
    {
        if(x == 0) return "0";
        string str = "";
        while(x)
        {
            int tmp = x % 10;
            x /= 10;
            str += '0' + tmp;
        }
        reverse(str.begin(), str.end());
        return str;
    }


    string solveEquation(string equation) {
        int cnt1 = 0, cnt2 = 0, f = 0, s;
        int len = equation.length();
        string str;
        int i = 0;
        while(i < len)
        {
            s = 0;

            str = "0";
            if(equation[i] == '=')
            {
                f = 1;
                i++;
            }
            if(equation[i] == '-')
            {
                s = 1;
                i++;
            }
            else if(equation[i] == '+') i++;
            if(f == 1)
            {
                while(equation[i] >= '0' && equation[i] <= '9') str += equation[i++];
                if(equation[i] == 'x')
                {
                    if(s == 0) cnt2 -= change(str);
                    else cnt2 += change(str);
                    i++;
                }
                else 
                {
                    if(s == 0) cnt1 += change(str);
                    else cnt1 -= change(str);
                }
            }
            else
            {
                while(equation[i] >= '0' && equation[i] <= '9') str += equation[i++];
                if(equation[i] == 'x')
                {
                    if(s == 0) cnt2 += change(str);
                    else cnt2 -= change(str);
                    i++;
                }
                else 
                {
               //     cout << str << endl;
                    if(s == 0) cnt1 -= change(str);
                    else cnt1 += change(str);
                }
            }


        }
       // cout << cnt2 << "  " << cnt1 << endl;
        if(cnt2 == 0)
            if(cnt1 == 0) str = "Infinite solutions";
            else str = "No solution";
        else
        {
            str = "x=";
            int tmp = cnt1 / cnt2;
            if(tmp < 0) str += '-', tmp = -tmp;
          // cout << tmp << endl;
            str += rev(tmp);
        }
        return str;






    }
};