（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?

 1 #include<stdio.h>
 2 #include<math.h>
 3 #include<string.h>
 4 #include<ctype.h>
 5 #include<stdlib.h>
 6 #include<stdbool.h>
 7 
 8 bool isprim(int n)
 9 {
10     int i=2;
11     if(n==1) return false;
12     for(; i*i<=n; i++)
13     {
14         if(n%i==0)  return false;
15     }
16     return true;
17 }
18 
19 bool pandigital(int n)
20 {
21     char s[10],d[10]={0};
22     int i=0;
23     sprintf(s,"%d",n);
24     int len=strlen(s);
25     while(i<len)
26     {
27         switch(s[i]-'0')
28         {
29             case 1: d[1]++;break;
30             case 2: d[2]++;break;
31             case 3: d[3]++;break;
32             case 4: d[4]++;break;
33             case 5: d[5]++;break;
34             case 6: d[6]++;break;
35             case 7: d[7]++;break;
36             case 8: d[8]++;break;
37             case 9: d[9]++;break;
38             default: break;
39         }
40         i++;
41     }
42     for(i=1; i<=len; i++)
43     {
44         if(d[i]!=1)  return false;
45     }
46     if(!isprim(n))  return false;
47     else return true;
48 }
49 
50 int main()
51 {
52     int i=10000001;
53     while(i>1000)
54     {
55         if(pandigital(i))
56         {
57             printf("%d\n",i);
58             break;
59         }
60         i=i-2;
61     }
62     return 0;
63 }

 

Answer:
 7652413

 

posted @ 2013-07-26 20:03  cpoint  阅读(366)  评论(0)  编辑  收藏  举报
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