8.cpp

// simple.cpp
class Solution {
public:
  int myAtoi(string str) {
    int len = str.size();
    if (len == 0)
      return 0;
    int i, j;
    for (j = 0; j < len && str[j] == ' '; ++j)
      ;
    int sign = 1;
    if (str[j] == '-' || str[j] == '+') {
      sign = str[j] == '-' ? -1 : 1;
      ++j;
    }
    if (!(str[j] >= '0' && str[j] <= '9'))
      return 0;
    for (i = j; i < len; ++i)
      if (!(str[i] >= '0' && str[i] <= '9'))
        break;
    int result = 0;
    while (j < i) {
      result = result * 10 + str[j++] - '0';
      if ((result > INT_MAX / 10 && j < i) ||
          (result == INT_MAX / 10 && j < i && str[j] > '7'))
        return sign == 1 ? INT_MAX : INT_MIN;
    }
    return sign * result;
  }
};