1005 - Rooks
Topic: combinatorics + Binomial Coefficient
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| #include<bits/stdc++.h> | |
| using namespace std; | |
| typedef long long ll; | |
| ll nCr(int n, int k) | |
| { | |
| ll ans[n+1][k+1]; | |
| int i,j; | |
| for(int i = 0; i <= n; i++){ | |
| for(int j = 0; j <= min(i,k); j++){ | |
| if(j == 0 || j == i) | |
| ans[i][j] = 1; | |
| else{ | |
| ans[i][j] = ans[i-1][j-1] + ans[i-1][j]; | |
| } | |
| } | |
| } | |
| return ans[n][k]; | |
| } | |
| int main() | |
| { | |
| int T; | |
| scanf("%d", &T); | |
| for(int cs = 1; cs <= T; cs++) | |
| { | |
| ll n,k; | |
| cin >> n >> k; | |
| ll res = nCr(n,k); | |
| for(int i =0; i < k; i++){ | |
| res *= n; | |
| n--; | |
| } | |
| printf("Case %d: ",cs); | |
| cout << res << endl; | |
| } | |
| return 0; | |
| } |
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