Description
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.
思路
- 这个题好像也没有什么简便方法，注意边界条件吧
代码
- 时间复杂度：O(n)
class Solution {
public:
const int min_int = -2147483648;
const int max_int = 2147483647;
int myAtoi(string str) {
int len = str.size();
if(len == 0) return 0;
int i = 0;
while(i < len && str[i] == ' ') i++;
bool isSymbol = false;
bool isNegative = false;
if(i < len && str[i] == '-'){
isSymbol = true;
isNegative = true;
i++;
}
if(!isSymbol && str[i] == '+'){
isSymbol = true;
i++;
}
if(i < len && str[i] >= '0' && str[i] <= '9'){
long long sum = 0;
while(i < len && str[i] >= '0' && str[i] <= '9'){
sum = sum * 10 + (str[i] - '0');
if(sum > max_int){
if(isNegative) return min_int;
return max_int;
}
i++;
}
return isNegative ? -sum : sum;
}
else return 0;
}
};内容来源于网络如有侵权请私信删除
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