[LeetCode] String to Integer (atoi)

代码：

class Solution {
public:
    int atoi(string str) {
        int num = 0;
        int sign = 1;
        const int n = str.size();
        int i = 0;

        while (str[i] == ' ' && i < n)
            i++;

        if (str[i] == '+') {
            i++;
        }
        else if (str[i] == '-') {
            sign = -1;
            i++;
        }

        if (str[i] == '+' || str[i] == '-')
            return 0;


        for (; i < n; i++) {
            if (str[i] < '0' || str[i] > '9')
                return num * sign;
            if (num > INT_MAX / 10 || (num == INT_MAX / 10 && (str[i] - '0') > INT_MAX % 10) ){
                return sign == -1 ? INT_MIN : INT_MAX;
            }
            num = num * 10 + str[i] - '0';
        }
        return num * sign;
    }
};

class Solution {
public:
    int atoi(string str) {
        int num = 0;
        int sign = 1;
        const int n = str.size();
        int i = 0;

        while (str[i] == ' ' && i < n)
            i++;

        if (str[i] == '+') {
            i++;
        }
        else if (str[i] == '-') {
            sign = -1;
            i++;
        }

        if (str[i] == '+' || str[i] == '-')
            return 0;


        for (; i < n; i++) {
            if (str[i] < '0' || str[i] > '9')
                return num * sign;
            if (num > INT_MAX / 10 || (num == INT_MAX / 10 && (str[i] - '0') > INT_MAX % 10) ){
                return sign == -1 ? INT_MIN : INT_MAX;
            }
            num = num * 10 + str[i] - '0';
        }
        return num * sign;
    }
};

杂记：

1. 纯粹的细节题，但是感觉好多细节不明。