Training1整数算法训练

#include <stdio.h>

int count(int n)
{
int i;
int m;
int temp;
int k = 0;

for(i = 9; i <= n; i++)
{
temp = i;
while(temp)
{
m = temp % 10;
temp /= 10;
if(m == 9)
{
k++;
}
}
}
return k;
}
int main()
{
int n;
int cnt;

printf("enter n: \n");
scanf("%d", &n);

cnt = count(n);

printf("1-%d has %d 9\n", n, cnt);
return 0;
}

#include <stdio.h>

int fun(int n)
{
int i;
int tmp;
int out = 0;
int num = 0;
int a[100] = {0};

for(i = 0; i < n; i++)
{
a[i] = 1;
}
i = 0;
while(out != n - 1)
{
if(a[i] == 1)
{
num++;
}
if(num == 3)
{
a[i] = 0;
num = 0;
out++;
}
i++;
if(i ==  n)
{
i = 0;
}

}
for(i = 0; i < n; i++)
{
if(a[i] == 1)
{
tmp = i + 1;
}
}
return tmp;
}

int main()
{
int n;
int last;

printf("enter the number of people:\n");
scanf("%d", &n);

last = fun(n);

printf("the last people is %d\n", last);

return 0;
}

#include <stdio.h>

int rank(double *b, int n)
{
int i, j;
int temp;

for(i = 0; i < n; i++)
{
for(j = i + 1; j < n; j++)
{
if(*(b + i) > *(b + j))
{
temp = *(b + i);
*(b + i) = *(b + j);
*(b + j) = temp;
}

}
}
}

int main()
{
double a[20];
int i = 0;
int j = 0;
char ch = 0;

printf("enter 20 numbers:\n");

while(ch != '\n')
{
scanf("%lf", a + i);
i++;
ch = getchar();
}
rank(a, i);
for(j = 0; j < i; j++)
{
printf("%lf", a[j]);
}
printf("\n");
return 0;
}

#include <stdio.h>
#include <math.h>

void prime(int n)
{
int i, j, flag;
int m = 0;
for(i = 1; i <= n; i++)
{
flag = 0;
for(j = 2; j <= sqrt(i); j++)
{
if(i % j == 0)
{
flag = 1;
}
}
if(flag == 0)
{
printf("%5d", i);
m++;
if(m % 5 == 0)
{
printf("\n");
}
}
}
}
int main()
{
int n = 100;

printf("the prime numbers between 1-100 are:\n" );
prime(n);
printf("\n");

return 0;
}