把字符串转换成整数

Posted 2022-01-27 骆驼绵羊

https://leetcode-cn.com/problems/ba-zi-fu-chuan-zhuan-huan-cheng-zheng-shu-lcof/

  public int strToInt(String str) 
        if (str == null || str.length() == 0 || str.trim().length() == 0) 
            return 0;
        
        int max = Integer.MAX_VALUE;
        //2147483647
        String trim = str.trim();
        int negative = 1;
        int ans = 0;

        if (trim.charAt(0) == '-') 
            negative = -1;
            trim = trim.substring(1);
         else if (trim.charAt(0) == '+') 
            trim = trim.substring(1);
        

        int length = trim.length();

        for (int i = 0; i < length; i++) 
            //重点是如何处理溢出问题
            if (trim.charAt(i) >= '0' && trim.charAt(i) <= '9') 
                if (ans > max / 10) 
                    if (negative == -1) 
                        return Integer.MIN_VALUE;
                    
                    return Integer.MAX_VALUE;
                 else if (ans == max / 10 && trim.charAt(i) > '7') 
                    if (negative == -1) 
                        return Integer.MIN_VALUE;
                    
                    return Integer.MAX_VALUE;
                
                ans = ans * 10 + (trim.charAt(i) - '0');
             else 
                break;
            
        
        return ans * negative;