N7Reverse.java

/*
给出一个 32 位的有符号整数，你需要将这个整数中每位上的数字进行反转。

示例 1:
输入: 123
输出: 321

溢出输出 0
 */
package LeetCode;

public class N7Reverse {
    private static int solution(int x){

        String s = Integer.toString(x);
        s = new StringBuilder(s).reverse().toString();
        int result = 0;
        if(x<0){
            try {
                result = Integer.valueOf(s.substring(0, s.length() - 1))*-1;
            } catch (Exception e){

            }
        }else{
            try {
                result = Integer.valueOf(s);
            } catch (Exception e){
            }
        }
         return result;

    }
    public static void main(String[] args) {
        int x = 120;

        //first version -- too slow.
        //System.out.println(solution(x));

        int pop;
        int ans = 0;

        while(x!=0){
            pop = x%10; //取末尾
            if(ans>Integer.MAX_VALUE/10||(ans==Integer.MAX_VALUE/10 && pop>7))
                //return 0;
                System.out.println(0);
            if(ans<Integer.MIN_VALUE/10 || (ans ==Integer.MIN_VALUE/10 && pop<-8))
                // return 0
                System.out.println(0);
            ans = ans*10+pop;
            x = x/10;
        }

        System.out.println(ans);

    }
}