题目:
http://codeforces.com/problemset/problem/520/C
题意:
长度为n 的字符串, 与只含有"ACGT"的n长度的字符串作比较,求出得到得数最大的字符串有几条.
思路:
求出字符串中重复次数最多的字母的个数x , 则答案为 ans = x ^ n.
AC.
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
const int mod = 1e9+7;
char s[100005];
int a[5];
long long cal(long long x, int n)
{
long long ans = 1;
while(n > 0) {
if(n & 1) ans = (ans * x) % mod;
x = (x * x) % mod;
n >>= 1;
}
return ans;
}
int main()
{
//freopen("in", "r", stdin);
int n;
while(~scanf("%d", &n)) {
scanf("%s", s);
memset(a, 0, sizeof(a));
for(int i = 0; i < n; ++i) {
if(s[i] == 'A') a[0]++;
if(s[i] == 'C') a[1]++;
if(s[i] == 'G') a[2]++;
if(s[i] == 'T') a[3]++;
}
sort(a, a+4);
int maxn = a[3];
long long cnt = 0;
for(int i = 0; i < 4; ++i) {
if(a[i] == maxn) cnt++;
}
long long ans = cal(cnt, n);
printf("%I64d\n", ans);
}
return 0;
}