50道基础编程题

1、输入3个数，求最大值

int main()
{ int a,b,c,m;
cin>>a>>b>>c;
m=a;
if(b>m) m=b;
if(c>m) m=c;
cout<<m;
}

2、编程序，求方程ax2+bx+c=0的根

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
double a, b, c, d, x1, x2;
cin >> a >> b >> c;
if (a == 0)
if (b == 0) cout << "error\n";
else cout << "x=" << -c / b << endl;
else
{
d = b * b - 4 * a*c;
if (fabs(d) <= 1e-6)
cout << "x1=x2=" << -b / (2 * a) << endl;
else if (d > 1e-6)
{
x1 = (-b + sqrt(d)) / (2 * a);
x2 = (-b - sqrt(d)) / (2 * a);
cout << "x1=" << x1 << ",x2=" << x2 << endl;
}
else cout << "方程无实根\n";
}
return 0;
}

3、输入一个成绩，打印相应的等级

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
int score;
cin >> score;
switch (score / 10)
{
case 10:
case 9:cout << "A" << endl; break;
case 8:cout << "B" << endl; break;
case 7:cout << "C" << endl; break;
case 6:cout << "D" << endl; break;
default:cout << "E" << endl; break;
}
return 0;
}

4、输入3个double类型的值，判断这3个值是否可以表示一个三角形的三条边。

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
double a, b, c;
cin >> a >> b >> c;
if (a + b > c&&a + c > b&&b + c > a)
cout << "可以构成三角形" << endl;
else
cout << "不能构成三角形" << endl;
return 0;
}

5、输入20个数，求其最大、最小和平均值

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
int a[20];
double sum = 0;
for (int i = 0; i < 20; i++)
{
cout << i + 1 << " ";
cin >> a[i];
sum += a[i];
}
sort(a, a + 20);
cout << "max=" << a[19] << endl;
cout << "min=" << a[0] << endl;
cout << "average=" << sum / 20 << endl;
return 0;
}

6、输入若干个数，设输入的第一个数为后面要输入的数的个数，求平均值及最大值。

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
int n, max, temp;
double sum = 0;
cin >> n;
cin >> temp;
max = temp;
sum = temp;
for (int i = 1; i < n; i++)
{
cin >> temp;
if (temp > max)
max = temp;
sum += temp;
}
cout << "平均值：" << double(sum) / n << endl;
cout << "最大值：" << max << endl;
return 0;
}

7、输入若干个数，输入-999表示结束，求平均值及最大值。

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
int n, cnt = 0;
double max, sum = 0;
cin >> n;
if (n != -999)
{
sum = n;
max = n;
cnt++;
}
while (cin >> n)
{
if (n == -999)
break;
if (n > max)
max = n;
sum += n;
cnt++;
}
cout << "最大值：" << max << endl;
cout << "平均值：" << sum /double(cnt) << endl;
return 0;
}

8、求和 s=11 + 22 + 33 +…+ 100100

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
double sum = 0;
for (int i = 1; i <= 100; i++)
{
sum += i * i;
}
cout << sum << endl;
return 0;
}

9、印度国王的奖励

int main()
{ double t=1,s=0;
for(int i=0; i<=63; i++)
{ s=s+t;
t=2*t;
}
cout<<s/1.4e8<<endl;
}

10、求和 s=1! + 2! + 3! +…+ 10!

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int fun(int n)
{
if (n == 1)
return 1;
else
return n * fun(n - 1);
}
int main()
{
long sum = 0;
for (int i = 1; i <= 10; i++)
sum += fun(i);
cout << sum << endl;
return 0;
}

11、求 e=1 + 1/1! + 1/2! + 1/3! + …（前20项）

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int fun(int n)
{
if (n == 1)
return 1;
else
return n * fun(n-1);
}
int main()
{
double e = 0;
for (int i = 1; i <= 20; i++)
{
e += double(1) / fun(i);
}
cout << e << endl;
return 0;
}

12、求PI值，PI/4 = 1 - 1/3 + 1/5 - 1/7 + …

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
double pi = 0,t=1;
int s = 1;
int i = 1;
while(fabs(t)>1e-18)
{
pi += t;
s = -s;
i = i + 2;;
t = double(s) / i;
}
cout << 4*pi << endl;
return 0;
}

14、输入20个数，统计其中正数、负数和零的个数。

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
int a = 0, b = 0, c = 0, n;
for (int i = 0; i < 20; i++)
{
cout << i + 1 << ": ";
cin >> n;
if (n == 0)
c++;
else if (n > 0)
a++;
else
b++;
}
cout << "正数：" << a << endl;
cout << "负数：" << b << endl;
cout << "零：" << c << endl;
return 0;
}

15、输入若干个整数，计算其中的奇数之和与偶数之和，假设输入0表示结束

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int main()
{
int a = 0, b = 0;
int n;
while (cin >> n)
{
if (n == 0)
break;
if (n % 2 == 0)
a += n;
else
b += n;
}
cout << "偶数之和：" << a << endl;
cout << "奇数之和：" << b << endl;
return 0;
}

16、写一函数，计算x的y次方（假设x、y都为正整数）。

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int pow(int x, int y)
{
int s = 1;
for (int i = 1; i <= y; i++)
s = s * x;
return s;
}
int main()
{
int x, y;
cin >> x >> y;
cout << "x的y次方=" << pow(x, y) << endl;
return 0;
}

17、求水仙花数（一个三位数，其各位数字立方和等于该数字本身）

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

bool fun(int n)
{
int a = n % 10;//个位数
int b = n / 10 % 10;//十位数
int c = n / 100; //百位数
if (n == (a*a*a + b * b*b + c * c*c))
return true;
return false;
}

int main()
{
int cnt = 0;
for(int i=100;i<=999;i++)
if (fun(i)) {
cout << i << '\t';
cnt++;
if (cnt % 5 == 0)
cout << endl;
}
return 0;
}

18、编写一个函数，确定一个整数是否为完全数（一个数，等于他的因子之和）。用这个函数确定和打印1到1000之间的所有完全数。

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

bool fun(int n)
{
int s = 0;
for (int i = 1; i <= n / 2; i++)
if (n%i == 0)
s += i;
if (s == n)
return true;
return false;
}
int main()
{
for (int i = 2; i <= 1000; i++)
if (fun(i))
cout << i << endl;

return 0;
}

19、写一函数，求斐波那契数列的第n项。

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int fun(int n)
{
if (n == 1 || n == 2)
return 1;
else
return fun(n - 1) + fun(n - 2);
}

int main()
{
int sum = 0;
for (int i = 1; i <= 20; i++)
{
cout << fun(i) << '\t';
if (i % 5 == 0)
cout << endl;
}
return 0;
}

20、写一个函数，取一个整数值并返回将此整数的各数字反序的数值

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int fun(int n)
{
int s = 0;
while (n)
{
s = s * 10 + n % 10;
n = n / 10;
}
return s;
}

int main()
{
int n;
cin >> n;
cout << fun(n) << endl;
return 0;
}

21、写一个函数，将一个整数的各位数字的反序打印

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

void fun(int n)
{
while (n)
{
cout<< n % 10<<" ";
n = n / 10;
}
cout << endl;
}

int main()
{
int n;
cin >> n;
fun(n);
return 0;
}

22、写一个函数，将一个整数的各位数字的按顺序打印出来

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

//数组方法
void show(int n)
{
int a[10], i = 0;
while (n)
{
a[i++] = n % 10;
n = n / 10;
}
for (int j = i - 1; j >= 0; j--)
cout << a[j] << " ";
cout << endl;
}
//递归
void show1(int n)
{
if (n < 10)
cout << n << endl;
else {
show1(n/10);
cout << n % 10 << " ";
}
cout << endl;
}
int main()
{
int n;
cin >> n;
cout << "数组存储方法：" << endl;
show(n);
cout << "递归方法：" << endl;
show(n);
return 0;
}

23、求一个整数的各位数之和的函数

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int fun(int n)
{
int s = 0;
while (n)
{
s += n % 10;
n = n / 10;
}
return s;
}
int main()
{
int n;
cin >> n;
cout << fun(n) << endl;
return 0;
}

24、写一函数，判断某个数是否素数，以及求1－1000之内的素数

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

bool isprime(int n)
{
for (int i = 2; i <= sqrt(n); i++)
if (n%i == 0)
return false;
return true;
}
int main()
{
int cnt = 0;
for (int i = 1; i <= 1000; i++)
{
if (isprime(i)) {
cnt++;
cout << i << '\t';
if (cnt % 5 == 0)cout << endl;
}
}
return 0;
}

25、用筛法求1－1000之内的素数

#include<iostream>
#include<cmath>
#include<stdlib.h>
#include<iomanip>
using namespace std;
int main()
{
int i,k,a[1001];
for(i=2; i<=1000; i++) a[i]=1;
float s=sqrt(float(1000));
for(i=2; i<=s; i++)
if(a[i]==1)
{ k=2*i;
while(k<=1000)
{ a[k]=0;
k=k+i;
}
}
for(i=2; i<=1000; i++)
if(a[i]==1) cout<<setw(5)<<i;
}

26、判断某一年是否闰年的函数

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

bool IsLeapYear(int y)
{
if (y % 400 == 0 || y % 4 == 0 && y % 100 != 0)
return true;
return false;
}
int main()
{
int year;
cin >> year;
if (IsLeapYear(year))
cout << year << "是闰年！" << endl;
else
cout << year << "不是闰年！" << endl;
return 0;
}

27、写一个函数，交换两个整型变量的值

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

void swap(int &a, int &b)
{
int t;
t = a;
a = b;
b = t;
}
int main()
{
int a, b;
cout << "输入a和b：" << endl;
cin >> a >> b;
swap(a, b);
cout << "交换后的a和b：" << endl;
cout << a << " " << b << endl;
return 0;
}

28、求两个数的最大公约数,欧几里德算法(辗转相除法）

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int gcd(int a, int b)
{
if (a%b == 0)
return b;
else
return gcd(b, a%b);
}
int main()
{
int a, b;
cin >> a >> b;
cout << "最大公约数：" << gcd(a, b) << endl;
return 0;
}

29、求两个数的最小公倍数

#include <iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int gcd(int a, int b)
{
if (a%b == 0)
return b;
else
return gcd(b, a%b);
}
int main()
{
int a, b;
cin >> a >> b;
cout << "最小公倍数：" << a*b/gcd(a, b) << endl;
return 0;
}

30、百钱买百鸡问题：鸡翁一值钱五，鸡母一值钱三，鸡雏三值钱一，百钱买百鸡，问鸡翁、母、雏各几何？

int main()
{
int cock,hen,chick;
for(cock=0; cock<=20; cock++)
for(hen=0; hen<=33; hen++)
{ chick=100-cock-hen;
if(5*cock+3*hen+chick/3.0==100)
cout<<setw(4)<<cock<<setw(4)<<hen <<setw(4)<<chick<<endl;
}
}

31、编一程序，输入一行字符串，统计其中的小写英文字母的个数。

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
using namespace std;

int main()
{
int cnt = 0;
string s;
cin >> s;
for (int i = 0; i < s.size(); i++)
{
if (s[i] >= 'a'&&s[i] <= 'z')
cnt++;
}
cout << "小写字母个数：" << cnt << endl;
}

32、编一程序，输入一行字符串，将其中的大写英文字母改为小写，再输出。

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
using namespace std;

int main()
{
int cnt = 0;
string s;
cin >> s;
for (int i = 0; i < s.size(); i++)
{
if (s[i] >= 'A'&&s[i] <= 'Z')
s[i] += 32;
}
cout << s<< endl;
}

33、打印杨辉三角形（帕斯卡三角形），打印10行。

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
using namespace std;

int main()
{
int a[10][10] = { 0 };
for (int i = 0; i < 10; i++)
{
a[i][0] = 1;
a[i][i] = 1;
}
for(int i=2;i<10;i++)
for (int j = 1; j <= i; j++)
{
a[i][j] = a[i - 1][j - 1] + a[i - 1][j];
}
for (int i = 0; i < 10; i++) {
for (int j = 0; j <= i; j++)
cout << a[i][j] << " ";
cout << endl;
}
return 0;
}

34、打印一个九九乘法表

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
using namespace std;

int main()
{
for (int i = 1; i <= 9; i++)
{
for (int j = 1; j <=i; j++)
cout << i << "*" << j << "=" << i * j << " ";
cout << endl;
}
return 0;
}

35、掷骰子10000次，统计得到各点数的次数。

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

int main()
{
int a[7] = { 0 };
srand(time(NULL));
for (int i = 1; i <= 10000; i++)
++a[rand() % 6 + 1];
for (int i = 1; i <= 6; i++)
cout << i << ":" << a[i] << endl;
return 0;
}

36、编写函数distance，计算两点(x1,y1)和(x2,y2)之间的距离。

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

double distance(double x1, double y1, double x2, double y2)
{
return sqrt((x1 - x2)*(x1 - x2) + (y1 - y2)*(y1 - y2));
}

int main()
{
double x1, x2, y1, y2;
cout << "输入两点" << endl;
cin >> x1 >> y1 >> x2 >> y2;
cout << distance(x1, x2, y1, y2) << endl;
return 0;
}

37、写一个程序，进行体操评分，依次输入10名评委所评分数，去除一个最高分和一个最低分，再算出平均分作为选手的得分。

int main()
{ int i;
float max,min,s,x;
max = 0; min = 10; s=0;
for(i=1;i<=10;i++)
{ cin >> x;
s = s + x;
if(x<min) min = x;
if(x>max) max = x;
}
s = s - min - max;
cout << s/8;
}

38、写一函数，将一数组中的元素反转。

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

void reverse(int a[], int n)
{
int t;
for (int i = 0; i < n / 2; i++)
{
t = a[i];
a[i] = a[n - i - 1];
a[n - i - 1] = t;
}
}

int main()
{
int a[100];
int n;
cin >> n;
for (int i = 0; i < n; i++)
cin >> a[i];
reverse(a, n);
for (int i = 0; i < n; i++)
{
cout << a[i] << " ";
}
cout << endl;
return 0;
}

39、写一函数，在一个数组中找出最大元素的位置

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

int fun(int a[], int n)
{
int max=a[0], x;
for (int i = 0; i < n; i++)
{
if (a[i] > max)
{
max = a[i];
x = i;
}
}
return x;
}

int main()
{
int n, a[100];
cin >> n;
for (int i = 0; i < n; i++)
cin >> a[i];
cout << "最大值的位置："<<fun(a, n) << endl;
return 0;
}

41、写一个字符串拷贝函数

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

void strcp(char *p, const char *q)
{
while (*p = *q)
{
p++;
q++;
}
}
int main()
{
char a[20] = "hello world!";
char b[20];
strcp(b, a);
cout << b << endl;
return 0;
}

42、写一个字符串比较函数

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

int cmp(char *a, char *b)
{
while (*a&&*b&&*a == *b)
{
a++;
b++;
}
return *a - *b;
}
int main()
{
char a[20] = "hello world!";
char b[20] = "hello !";
cout << cmp(a, b) << endl;
return 0;
}

43、写一个字符串连接函数

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

char *str(char *a, char *b)
{
char *p = a;
while (*a)a++;
while (*a++ = *b++);
*a = '\0';
return p;
}
int main()
{
char a[100] = "hello world!";
char b[20] = "my name is Lily";
cout << str(a, b) << endl;
return 0;
}

44、写一个求字符串长度函数

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

int len(char *a)
{
int len = 0;
while (*a)
{
len++;
a++;
}
return len;
}
int main()
{
char a[20] = "hello world!";
cout << "hello world!长度：" << len(a) << endl;
return 0;
}

45、写一函数，在一数组里查找某个值。

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

int search(int a[], int n, int key)
{
for (int i = 0; i < n; i++)
if (a[i] == key)
return i;
return -1;
}
int main()
{
int n, a[100];
cin >> n;
for (int i = 0; i < n; i++)
cin >> a[i];
cout << "输入你要搜索的关键词：" << endl;
int key;
cin >> key;
cout << "key的位置：" << search(a, n, key);
return 0;
}

46、编一程序，求两个矩阵的乘积

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

int main()
{
int a[3][3], b[3][3], c[3][3];
for (int i = 0; i < 3; i++)
for (int j = 0; j < 3; j++)
cin >> a[i][j];
for (int i = 0; i < 3; i++)
for (int j = 0; j < 3; j++)
cin >> b[i][j];
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
int sum = 0;
for (int k = 0; k < 3; k++)
{
sum += a[i][k] * b[k][j];
}
c[i][j] = sum;
}
}
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++)
cout << c[i][j] << " ";
cout << endl;
}
return 0;
}

47、计算某日是某年的第几天

#include <iostream>
#include<algorithm>
#include<cmath>
#include<string>
#include<ctime>
using namespace std;

bool fun(int y)
{
if (y % 400 == 0 || y % 4 == 0 && y % 100 != 0)
return true;
return false;
}
int main()
{
int y;
cin >> y;
if (fun(y))
cout << y << "是闰年！" << endl;
else
cout << y << "不是闰年！" << endl;

return 0;
}

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