C. DNA Alignment
time limit per test
memory limit per test
input
output
Vasya became interested in bioinformatics. He's going to write an article about similar cyclic DNA sequences, so he invented a new method for determining the similarity of cyclic sequences.
s and t have the same length n, then the function h(s, t) is defined as the number of positions in which the respective symbols of s and t are the same. Function h(s, t) can be used to define the function of Vasya distance ρ(s, t):
where
is obtained from string
s, by applying left circular shift
i times. For example,
ρ("AGC", "CGT") =
h("AGC", "CGT") + h("AGC", "GTC") + h("AGC", "TCG") +
h("GCA", "CGT") + h("GCA", "GTC") + h("GCA", "TCG") +
h("CAG", "CGT") + h("CAG", "GTC") + h("CAG", "TCG") =
1 + 1 + 0 + 0 + 1 + 1 + 1 + 0 + 1 = 6 s of length n on the Internet. Now he wants to count how many strings t there are such that the Vasya distance from the string s attains maximum possible value. Formally speaking, t must satisfy the equation:
.
109.
Input
n (1 ≤ n ≤ 105).
n, consisting of characters "ACGT".
Output
109.
Examples
input
1C
output
1
input
2AG
output
4
input
3TTT
output
1
#include <bits/stdc++.h>
#define maxn 100005
#define MOD 1000000007
using namespace std;
typedef long long ll;
char str[maxn];
int d[30];
int main(){
// freopen("in.txt", "r", stdin);
int n;
scanf("%d%s", &n, str);
for(int i = 0; str[i]; i++){
d[str[i]-'A']++;
}
ll maxs = 0, cnt = 0;
for(int i = 0; i < 30; i++){
if(d[i] > maxs){
maxs = d[i];
cnt = 1;
}
else if(d[i] && d[i] == maxs){
cnt++;
}
}
ll ans = 1;
while(n--){
(ans *= cnt) %= MOD;
}
printf("%I64d\n", ans);
return 0;
}
