> #include <stdio.h>
> #include <string.h>
> 
> char f[3][2][400] = {{"0", "1"}, {"0", "1"}, 0};
> char temp[400] = {0}, tmp[400] = {0};
> int n;
> int max(int a, int b)
> {
>     if (a > b) return a;
>     else  return b;
> }
> void fix(char *s)
> {
>      int i, len = strlen(s);
>      char t;
>      for (i = 0; i < len/2; i++)
>      {
>          t = s[i];
>          s[i] = s[len-1-i];
>          s[len-1-i] = t;
>      }
> }
> char *add(char *s1, char *s2)
> {
>      int i, c, len, len1 = strlen(s1), len2 = strlen(s2);
>      fix(s1);
>      fix(s2);
>      len = max(len1, len2);
>      for (i = len1; i < len; i++)      s1[i] = '0';
>      for (i = len2; i < len; i++)      s2[i] = '0';
>      memset(temp, 0, sizeof(temp));
>      for (c = i = 0; i < len; i++)
>      {
>          c += ((s1[i]-'0')+(s2[i]-'0'));
>          temp[i] = (char)(c%10+'0');
>          c /= 10;
>      }
>      if (c > 0)  temp[len++] = (char)(c+'0');
>      fix(temp);
>      fix(s1);
>      fix(s2);
>      return temp;
> }
> 
> int main()
> {
>     int i;
>     while (scanf("%d", &n) != EOF)
>     {
>           memset(f, 0, sizeof(f));
>           f[0][0][0] = f[1][0][0] = f[2][0][0] = '0';
>           f[0][1][0] = f[1][1][0] = f[2][1][0] = '1';
>           for (i = 2; i <= n; i++)
>           {
>               strcpy(f[2][0], add(f[0][0], f[0][1]));
>               strcpy(f[2][1], add(f[1][1], strcpy(tmp, f[1][1])));
>               strcpy(f[0][0], f[1][0]);
>               strcpy(f[0][1], f[1][1]);
>               strcpy(f[1][0], f[2][0]);
>               strcpy(f[1][1], f[2][1]);
>           }
>           printf("%s\n", f[2][0]);
>     }
>     //system("pause");
>     return 0;
> }
> 
> 试了N次，老是超时！我的递推公式是：  f[n]双0的对数 = (f[n-2]双0的对数） ＋ （f[n-2]中1的个数）


AC了！！！！！
#include <stdio.h>

int result[1001][401], n;

void compute(int a[], int c[], int n)
{
     int i, temp;
     memset(c, 0, sizeof(result[0]));
     if (n % 2 == 0)    c[1]++;
     else    c[1]--;
     for (i=1; i<=400; i++) {
         temp = a[i] + a[i] + c[i];
         if(temp < 0) {
                 temp += 10;
                 c[i] = temp % 10;
                 c[i+1]--;
                 continue;
         }
         c[i] = temp % 10;
         c[i+1] = temp / 10; 
     }
}

int main()
{
    int i, j;
    memset(result, 0, sizeof(result));
	for(i = 2; i<=1000; i++)         compute(result[i-1], result[i], i);
    while (scanf("%d", &n) != EOF) {
          if(n == 0) {
               printf("0\n");
               continue;
          }
          if(n == 1) {
               printf("0\n");
               continue;
          }
		  for(i=400; i>0; i--) 
                     if(result[n][i] != 0)   {
                             j = i;
                             break;
                     }
          for (; j > 0; j--)
				printf("%d", result[n][j]);
          printf("\n");
    }
    //system("pause");      
    return 0;
}