问题描述
https://leetcode.com/problems/string-to-integer-atoi/
解决思路
直接看代码吧，题目就是有点麻烦，不是很难，注释把思路写的够清晰了
代码
class Solution {
public int myAtoi(String str) {
//process the whitespace
str = str.trim();
//corner case
if(str == null || str.length() == 0) return 0;
char firstChar = str.charAt(0);
long res = 0;
int isPositive = 1;
int start = 0;
//process '+'/'-' occcurs in the begining
if(firstChar == '+') {
isPositive = 1;
start++;
} else if(firstChar == '-'){
isPositive = -1;
start++;
}
for(int i = start; i < str.length(); i++){
if(!Character.isDigit(str.charAt(i))){
return (int)(isPositive * res);
}
//count the res
res = res * 10 + (str.charAt(i) - '0');
//out the range
if(isPositive == 1 && res > Integer.MAX_VALUE) return Integer.MAX_VALUE;
if(isPositive == -1 && res > Integer.MAX_VALUE) return Integer.MIN_VALUE;
}
return (int)(isPositive * res);
}
}
效率探究
时间效率：O(n)
空间效率：O(1)
