[C++知识库]C++代码练习及答案

简单C++程序

#include<iostream>//预处理命令
using namespace std;//命名空间
int main() {
	
	cout << "Hello!" << endl;//输出
	cout << "Welcome to C++!" << endl;

	return 0;
}

输入一个年份，判断是否是闰年

#include<iostream>
using namespace std;
int main() {
	
	int year;
	bool isLeapYear;

	cout << "输入一个年份：" << endl;
	cin >> year;
	isLeapYear = ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0));

	if (isLeapYear)
		cout << year << " is a leap year" << endl;
	else
	{
		cout << year << " is not a leap year" << endl;
	}

	return 0;
}

比较两个数的大小

#include<iostream>
using namespace std;

int main() {
	
	int x, y;
	cout << "Enter x and y:";
	cin >> x >> y;

	if (x != y)
		if (x > y)
			cout << "x>y" << endl;
		else
		{
			cout << "x<y" << endl;
		}
	else
	{
		cout << "x=y" << endl;
	}

	return 0;
}

输入一个0~6的整数，转换成星期输出

#include<iostream>
using namespace std;

int main() {
	
	int day;

	cin >> day;
	switch (day)
	{
	case 0:
		cout << "Sunday" << endl;
		break;
	case 1:
		cout << "Monday" << endl;
		break;
	case 2:
		cout << "Tuesday" << endl;
		break;
	case 3:
		cout << "Wednesday" << endl;
		break;
	case 4:
		cout << "Thursday" << endl;
		break;
	case 5:
		cout << "Friday" << endl;
		break;
	case 6:
		cout << "Saturday" << endl;
		break;
	default:
		cout << "Day out of range Sunday...Saturday" << endl;
		break;
	}

	return 0;
}

求1~10的之和

#include<iostream>
using namespace std;

int main() {
	
	int i = 1,sum = 0;
	while (i <= 10) {
		sum += i;
		i++;
	}
	cout << "sum=" << sum << endl;

	return 0;
}

输入一个整数，将各位数字反转后输出

#include<iostream>
using namespace std;

int main() {
	
	int n, right_digit, newnum = 0;
	cout << "Enter the number:";
	cin >> n;

	cout << "The number in reverse order is ";
	do {
		right_digit = n % 10;
		cout << right_digit;
		n /= 10;
	} while (n != 0);
	cout << endl;

	return 0;
}

用do…while语句编程，求自然数1~10之和

#include<iostream>
using namespace std;

int main() {
	
	int i = 1, sum = 0;
	do {
		sum += i;
		i++;
	} while (i < 10);
	cout << "sum=" << sum << endl;

	return 0;
}

输入一个整数，求出它的所有因子

#include<iostream>
using namespace std;

int main() {
	
	int n;

	cout << "Enter a postive integer:";
	cin >> n;
	cout << "Number " << n << " Factors ";

	for (int k = 1; k <= n; k++) {
		if (n % k == 0) {
			cout << k << " ";
		}
	}
	cout << endl;

	return 0;
}

编写输出图案

#include<iostream>
using namespace std;

int main() {
	
	const int N = 4;
	for (int i = 1; i <= N; i++) {
		for (int j = 1; j <= 30; j++) {
			cout << ' ' ;
		}
		for (int j = 1; j <= 8 - 2 * i; j++) {
			cout << ' ' ;
		}
		for (int j = 1; j <= 2 * i - 1; j++) {
			cout << '*';
		}
		cout << endl;
	}
	for (int i = 1; i <= N - 1; i++) {
		for (int j = 1; j <= 30; j++) {
			cout << ' ';
		}
		for (int j = 1; j <= 7 - 2 * i; j++) {
			cout << '*';
		}
		cout << endl;
	}

	return 0;
}

求100~200之间不能被3整除的数

#include<iostream>
using namespace std;

int main() {
	
	for (int n = 100; n <= 200; n++) {
		if (n % 3 != 0) {
			cout << n << endl;
		}
	}

	return 0;
}

读入一系列整数，统计出正整数个数i和负整数个数j，读入0则结束

#include<iostream>
using namespace std;

int main() {
	
	int i = 0, j = 0, n;
	cout << "Enter some integers please (enter 0 to quit):" << endl;
	cin >> n;
	while (n != 0) {
		if (n > 0) {
			i += 1;
		}
		if (n < 0) {
			j += 1;
		}
		cin >> n;
	}
	cout << "Count of positive integers:" << i << endl;
	cout << "Count of negative integers:" << j << endl;

	return 0;
}

设某次体育比赛只有4种可能，所以可以声明一个枚举类型，用一个枚举类型的变量来存放比赛比赛结果

#include<iostream>
using namespace std;

enum GameResult{WIN,LOSE,WIE,CANCEL};

int main() {
	
	GameResult result;//声明变量时，可以不写关键字enum
	enum GameResult omit = CANCEL;//也可以在类型名前写enum

	for (int count = WIN; count <= CANCEL; count++) {//隐式类型转换
		result = GameResult(count);//显式类型转换
		if (result == omit) {
			cout << "The game was cancelled" << endl;
		}
		else {
			cout << "The game was played";
			if (result == WIN) {
				cout << "and we won!";
			}
			if (result == LOSE) {
				cout << "and we lost.";
			}
			cout << endl;
		}
	}

	return 0;
}