CodeForces 520C 水构造

//520C - DNA Alignment

 1 #include "iostream"
 2 #include "cstdio"
 3 using namespace std;
 4 const __int64 mod = 1e9 + 7;
 5 int n;
 6 char str[100010];
 7 int Count[5];
 8
 9 __int64 bin(__int64 n, __int64 k)
10 {
11     __int64 res = 1;
12     while(k) {
13         if(k & 1)
14             res *= n, res %= mod;
15         n *= n;
16         n %= mod;
17         k >>= 1;
18     }
19     return res;
20 }
21
22 int main()
23 {
24     int i;
25     scanf("%d%s", &n, str + 1);
26     for(i = 1; i <= n; ++i) {
27         switch(str[i]) {
28         case ‘A‘:
29             ++Count[1];
30             break;
31         case ‘C‘:
32             ++Count[2];
33             break;
34         case ‘G‘:
35             ++Count[3];
36             break;
37         case ‘T‘:
38             ++Count[4];
39         }
40     }
41     int Max = max(max(Count[1], Count[2]), max(Count[3], Count[4]));
42     int Choice = 0;
43     for(i = 1; i <= 4; ++i)
44         if(Max == Count[i])
45             ++Choice;
46     printf("%I64d\n", bin(Choice, n));
47 }