LeetCode高频面试60天打卡日记Day34（字符串到整数）

Day34（字符串到整数）

class Solution {
    
    
    public int myAtoi(String str) {
    
    
        char[] chars = str.toCharArray();
        int n = chars.length;
        int cur = 0;
        //去掉前导空格
        while(cur<n && chars[cur]==' '){
    
    
            cur++;
        }
        if(cur==n){
    
    
            return 0;
        }

        boolean negative = false;
        if(chars[cur]=='-'){
    
    
            negative = true;
            cur++;
        }else if(chars[cur]=='+'){
    
    
            cur++;
        }else if(!Character.isDigit(chars[cur])){
    
    
            return 0;
        }
        
        int ans = 0;
        int digit = 0;
        while(cur<n && Character.isDigit(chars[cur])){
    
    
            digit = chars[cur]-'0';
            if(ans>(Integer.MAX_VALUE-digit)/10){
    
     //保证不溢出
                return ans = negative? Integer.MIN_VALUE:Integer.MAX_VALUE;
            }
            ans = ans*10+digit;
            cur++;
        }
        return negative?-ans:ans;
    }
}