Poj.Grids 2951 浮点数求高精度幂

 1 //@author langx
 2 //G++4.4
 3 #include <cstdio>
 4 #include <cstring>
 5 #define SIZE 126
 6 #define LEN 5
 7 
 8 int a[SIZE],b[LEN];
 9 
10 int mul( int alen,int blen){
11     int tmp[SIZE], i, j, k;
12     memset(tmp,0,sizeof(tmp));
13     for( i = 0; i < alen; ++i){
14         for( j = 0; j < blen; ++j){
15             tmp[i + j] += a[i] * b[j];
16         }   
17     }
18     k = alen + blen - 1;
19     for( i = 0;i < k; ++i){
20         if( tmp[i] >= 10){
21             tmp[ i + 1] += tmp[i] / 10;
22             tmp[i] = tmp[i] % 10;
23         }
24         a[i] = tmp[i];
25     }
26     a[i] = tmp[i];
27     if( tmp[k] !=0 )k++;
28     return k;
29 }
30 
31 int main(){
32     char r[LEN + 1];
33     int n, i, j, len, alen, mark, formark, ok;
34     while( scanf("%s%d",r, &n) == 2 ){
35         len = strlen(r);
36         mark = 0;
37         for( i = len - 1, j = 0 ; i >= 0 ; --i){
38             if(r[i]==‘.‘){
39                 mark =i;continue; //记录小数点位置
40             }
41             a[j] = b[j++] = r[i]-‘0‘;
42         }
43         --len;
44         mark = len - mark;
45         alen = len;
46         for( i = 1;i < n; i++){
47             alen = mul( alen,len);
48         }
49         for( i = 0; i < alen; ++i){
50             if( a[i] != 0)break;
51         }
52         mark *= n;
53         formark = i; //记录后缀，如70.10000
54         ok = 0;
55         for( i = alen-1; i >= formark; --i){
56             if( a[i] == 0 && i >= mark && !ok )continue;
57             if( i == mark - 1) printf(".");
58             printf("%d", a[i]);
59             ok = 1;
60         }
61         for(formark--; formark >= mark; --formark){
62             printf("0");
63         }
64         printf("\n");
65     }
66     return 0;
67 }