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* Implement atoi to convert a string to an integer.
* Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.
* Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.
*
* Requirements for atoi:
* The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.
* The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.
* If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.
* If no valid conversion could be performed, a zero value is returned. If the correct value is out of the range of representable values, INT_MAX (2147483647) or INT_MIN (-2147483648) is returned.
*/
publicclassStringToInteger {
/**
* 得有多无聊，才能有这样的题！！！
*/
classSolution {
publicintmyAtoi(Stringstr) {
if (str == null || str.length() == 0) {
return0;
}
longresult = 0;
char[] arr = str.toCharArray();
booleanflag = false;
inti = 0;
// 去除前导空格
while (i < arr.length && arr[i] == ' ') {
i++;
}
// 判断正负
if (i < arr.length) {
if (arr[i] == '-') {
flag = true;
i++;
} elseif (arr[i] == '+') {
i++;
}
}
if (i == arr.length) {
return0;
}
// 正负号后必须为数字
if (i + 1 < arr.length && !(arr[i] >= '0' && arr[i] <= '9')) {
