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70 lines
1.0 KiB
C++
70 lines
1.0 KiB
C++
#include <iostream>
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#include <string>
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#include <unordered_map>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = (18 << 1) + 5;
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int n;
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long long ans;
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bool vis[N];
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std::string s;
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std::unordered_map<std::string, int> map;
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void dfs1(int x) {
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if (x == n + 1) {
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std::string s1, s2;
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for (int i = 1; i <= n; i++) {
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(vis[i] ? s2 : s1).push_back(s[i]);
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}
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map[s1 + ' ' + s2]++;
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return;
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}
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dfs1(x + 1);
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vis[x] = true;
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dfs1(x + 1);
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vis[x] = false;
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}
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void dfs2(int x) {
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if (x == n * 2 + 1) {
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std::string s1, s2;
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for (int i = n + n; i > n; i--) {
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(vis[i] ? s2 : s1).push_back(s[i]);
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}
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ans += map[s1 + ' ' + s2];
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return;
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}
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dfs2(x + 1);
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vis[x] = true;
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dfs2(x + 1);
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vis[x] = false;
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> s;
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s = ' ' + s;
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dfs1(1);
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dfs2(n + 1);
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cout << (ans >> 1) << endl;
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return 0;
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}
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