7. 整数反转

class Solution {

public int reverse(int x) {
    int flag = 1;
    if(x < 0){
        flag = -1;
        x = x * flag;
    }
    double maxValue = Math.pow(2,31);
    double minValue = 0 - Math.pow(2,31);
    int result = 0;
    while(true) {
        int right = x % 10;//余数
        if(result > ((maxValue - 1) - right) / 10){
            return 0;
        }
        if(result < (minValue - right) / 10) {
            return 0;
        }
        result = result * 10 + right;
        //if(result > maxValue - 1)此处不能校验住，因为超界后，result是一个小于maxValue - 1的值
        x = x / 10;
        if(x == 0) {
            break;
        }
    }
    if(flag == -1){
        result = result * flag;
    }
    
    return result;
}

}