做入門題或許是有用的吧！

#include <stdio.h>

int main(void) {
	int A, count = 0, a;
	printf("請玩家1輸入一個1到100的整數：");
	scanf("%d", &A);
	while (A < 1 || A > 100) {
		printf("\n輸入的整數不在1到100之間，請重新輸入：");
		scanf("%d", &A);
	}
	do {
		printf("\n請玩家2輸入你猜的整數：");
		scanf("%d", &a);
		if(a > A) {
			printf("\n大\n");
		}
		if(a < A) {
			printf("\n小\n");
		}
		count++;
	} while (A != a);
	printf("\n猜中，猜了%d次\n", count);
}

#include <iostream>
using namespace std;

int main() {
	int a, b;
	char s[0xff], *p = s;
	cout << "請輸入一個整數：" << endl;
	cin >> a;
	while(a) {
		b = a % 10;
		*p++ = b + '0';
		a /= 10;
	}
	*p = '\0';
	cout << "整數的逆序是：" << endl;
	p = s;
	do {
		cout << *p++;
	} while(*p);
}