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       // 7. Reverse Integer// Difficulty: Easy// Reverse digits of an integer.// Example1: x = 123, return 321// Example2: x = -123, return -321// https://leetcode.com/problems/reverse-integer/int reverse(int x) {    // *** METHOD 2    long y = 0;            // a trick, may be improved    while (x) {        y = y * 10 + x % 10;        x /= 10;        if (y > pow(2,31) - 1 || y < -1 * pow(2,31)) {            printf("(2^31) - 1 = %d, -1 * (2^31) = %d, y = %ld\n", (int)pow(2,31) - 1, -1 * (int)pow(2,31), y);            return 0;    // IMPORTANT: consider range of int        }    }    return y;}int main() {    int x = 1534236469;    printf("x = %d, reversed x = %d\n", x, reverse(x));    return 0;}