50 lines
1.3 KiB
C++
50 lines
1.3 KiB
C++
#include <algorithm>
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#include <cstdio>
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#include <cstring>
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#include <deque>
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#include <fstream>
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#include <iostream>
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#include <list>
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#include <map>
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#include <queue>
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#include <set>
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#include <stack>
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#include <string>
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#include <vector>
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using namespace std;
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long long bishops(int n, int k)
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{
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long long r1[9];
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long long r2[9];
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for (int i = 1; i <= n; ++i)
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r1[i] = i % 2 != 0 ? i : r1[i-1];
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for (int i = 1; i <= n-1; ++i)
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r2[i] = i % 2 != 0 ? i+1 : r2[i-1];
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long long c1[9][65] = {{0}};
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long long c2[9][65] = {{0}};
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for (int i = 0; i <= n; ++i)
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c1[i][0] = 1;
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for (int j = 1; j <= k; ++j)
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c1[0][j] = 0;
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for (int i = 1; i <= n; ++i)
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for (int j = 1; j <= k && j <= i; ++j)
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c1[i][j] = c1[i-1][j] + c1[i-1][j-1]*(r1[i] - j + 1);
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for (int i = 0; i <= n-1; ++i)
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c2[i][0] = 1;
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for (int j = 1; j <= k; ++j)
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c2[0][j] = 0;
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for (int i = 1; i <= n-1; ++i)
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for (int j = 1; j <= k && j <= i; ++j)
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c2[i][j] = c2[i-1][j] + c2[i-1][j-1]*(r2[i] - j + 1);
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long long r = 0;
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for (int i = 0; i <= k; ++i)
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r += c1[n][i] * c2[n-1][k-i];
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return r;
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}
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int main(int argc, char *argv[])
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{
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for (int n, k; cin >> n >> k && !(n == 0 && k == 0); )
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cout << bishops(n, k) << endl;
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return 0;
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}
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