题目描述
Implement atoi to convent a string to an integer.
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.
输入与输出
class Solution {
public:
int myAtoi(string str) {
}
};
样例
题目中没有样例，提供一些测例。
| Input | Output |
|---|---|
| "" | 0 |
| "+" | 0 |
| "+-2" | 0 |
| "-+5" | 0 |
| " -0012a42" | -12 |
| "-2147483648" | -2147483648 |
| "2147483648" | 2147483647 |
题解与分析
功能自身不难实现，需要考虑较多的边界情况。（自己的实现不是很优雅>_<）
C++ 代码如下：
class Solution {
public:
int myAtoi(string str) {
if (str.empty())
return 0;
int index = 0;
long long num = 0;
bool negative = false;
while (str[index] == ' ')
++index;
if (str[index] == '+' || str[index] == '-')
negative = (str[index] == '-'), ++index;
for ( ; index < str.size() && str[index] >= '0' && str[index] <= '9'; ++index) {
num = num * 10 + str[index] - '0';
if (num > (long long)INT_MAX + 10)
break;
}
num = negative ? -num : num;
if (num > INT_MAX)
num = INT_MAX;
if (num < INT_MIN)
num = INT_MIN;
return num;
}
};
该解法的时间复杂度为 O(n)。
