32 lines
767 B
C++
32 lines
767 B
C++
#include <bits/stdc++.h>
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#define f first
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#define s second
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using namespace std;
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using ll = long long;
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using ii = pair<int, int>;
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constexpr int MX = 1e6+5;
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int p2[MX] = { 1 };
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int main() {
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if (fopen("in", "r")) freopen("in", "r", stdin), freopen("out", "w", stdout);
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ios_base::sync_with_stdio(0), cin.tie(0);
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int N, M; cin >> N >> M;
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string S; cin >> S;
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for (int i = 0; i < N; ++i) p2[i+1] = 2*p2[i]%M;
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int ans = 1, cnt = 0, l = 0, h = 0;
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for (int i = 0; i < N; ++i) {
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if (S[i] == 'P') {
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int a = min(cnt-1, l), b = max(cnt-1, h);
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if (abs(b-a) == 1) (ans += p2[(N-i-1)/2]+p2[(N-i)/2]-1) %= M;
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else if (abs(b-a) == 2) (ans += p2[(N-i-(cnt != a))/2]) %= M;
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}
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cnt += (S[i] == 'P' ? 1 : -1);
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l = min(cnt, l), h = max(cnt, h);
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}
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cout << ans;
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}
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