7. Reverse Integer

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

题目含义翻转一个整数

    public int reverse(int x) {
        int res = 0;
        while (x != 0) {
            if (Math.abs(res) > Integer.MAX_VALUE / 10) return 0; //防止接下来的res*10超过Integer.MAX_VALUE
            res = res * 10 + x % 10;
            x /= 10;
        }
        return res;        
    }

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