1
/*
(1)判断一个数是素数及查找begin和end之间的素数。
*/
//判断一个数是素数
#include <iostream>
#include <cmath>
using namespace std;
/*void isPrime(int num)
{
if(num < 2)
{
cout << num << "is not a prime." << endl;
return;
}
int temp = (int)sqrt(num);
for(int i = 2;i <= temp;i++)
{
if(num%i == 0)
{
cout << num << "is not a prime." << endl;
return;
}
}
if(i > temp)
cout << num << "is a prime." << endl;
}*/
//查找begin和end之间的素数.
void numberofPrime(int begin,int end)
{
int num;
if((begin == 1) || (begin == 2))
num = 2;
else if(begin % 2 == 0)
num = begin + 1;
else
num = begin;
for(;num <= end;num++)
{
if(num < 2)
{
cout << num << "is not a prime." << endl;
break;
}
int temp = (int)sqrt(num);
for(int i = 2;i <= temp;i++)
{
if(num%i == 0)
{
cout << num << "is not a prime." << endl;
break;
}
}
if(i > temp)
cout << num << "is a prime." << endl;
}
}
int main()
{
int begin,end;
while(cin >> begin >> end)
numberofPrime(begin,end);
return 0;
}
2
/*
b找出一个数组中大于等于元素平均值的元素个数。
【功能】:找出一个数组arr[]中大于等于平均值的元素个数
【输入】:数组arr[], 数组的元素个数n
【输出】:大于等于平均值的元素个数cnt
int func(int iArray[],int nSize).
*/
#include <iostream>
using namespace std;
int func(int arr[],int n)
{
int sum = 0, cnt = 0;
for(int i = 0;i < n;i++)
{
sum += arr[i];
}
double aver = (double)sum/n;
for(int j = 0;j < n;j++)
{
if(arr[j] >= aver)
cnt++;
}
return cnt;
}
int main()
{
int arr[6] = {2,2,3,4,5,6};
cout << func(arr,6) << endl;
return 0;
}
3
/*
3)判断一个整型数是否为“回文数”,如1221,232,5。
*/
#include <iostream>
using namespace std;
void isHuiwen(int number)
{
int m = number;
int n = 0;//余数.
while(m != 0)
{
n = n*10 + m%10;
m = m/10;
}
if(n - number == 0)
cout << "yes" << endl;
else
cout << "no" << endl;
}
int main()
{
int number;
while(cin >> number)
isHuiwen(number);
return 0;
}