（Problem 41）Pandigital prime

We shall say that an n-digit number is pandigital if it makes use of all the digits 1 to n exactly once. For example, 2143 is a 4-digit pandigital and is also prime.
What is the largest n-digit pandigital prime that exists?

#include<stdio.h>
#include<math.h>
#include<string.h>
#include<ctype.h>
#include<stdlib.h>
#include<stdbool.h>

bool isprim(int n)
{
	int i=2;
	if(n==1) return false;
	for(; i*i<=n; i++)
	{
		if(n%i==0)  return false;
	}
	return true;
}

bool pandigital(int n)
{
	char s[10],d[10]={0};
	int i=0;
	sprintf(s,"%d",n);
	int len=strlen(s);
	while(i<len)
	{
		switch(s[i]-'0')
		{
		    case 1: d[1]++;break;
		    case 2: d[2]++;break;
			case 3: d[3]++;break;
			case 4: d[4]++;break;
			case 5: d[5]++;break;
			case 6: d[6]++;break;
			case 7: d[7]++;break;
			case 8: d[8]++;break;
			case 9: d[9]++;break;
		    default: break;
		}
		i++;
	}
	for(i=1; i<=len; i++)
	{
		if(d[i]!=1)  return false;
	}
	if(!isprim(n))  return false;
	else return true;
}

int main()
{
	int i=10000001;
	while(i>1000)
	{
		if(pandigital(i))
		{
			printf("%d\n",i);
			break;
		}
		i=i-2;
	}
	return 0;
}

Answer:

7652413