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  • Light oj 1005

    题目链接:http://www.lightoj.com/volume_showproblem.php?problem=1005

    纸上画一下,找了一下规律,Ank*Cnk.

     1 //#pragma comment(linker, "/STACK:102400000, 102400000")
     2 #include <algorithm>
     3 #include <iostream>
     4 #include <cstdlib>
     5 #include <cstring>
     6 #include <cstdio>
     7 #include <vector>
     8 #include <cmath>
     9 #include <ctime>
    10 #include <list>
    11 #include <set>
    12 #include <map>
    13 using namespace std;
    14 typedef long long LL;
    15 typedef pair <int, int> P;
    16 const int N = 1e5 + 5;
    17 
    18 LL Anm(LL n, LL m) {
    19     LL ans = 1;
    20     for(LL i = n; i >= n - m + 1; --i) {
    21         ans = ans * i;
    22     }
    23     return ans;
    24 }
    25 
    26 int main()
    27 {
    28     int t;
    29     LL n, k;
    30     scanf("%d", &t);
    31     for(int ca = 1; ca <= t; ++ca) {
    32         scanf("%lld %lld", &n, &k);
    33         printf("Case %d: ", ca);
    34         if(k > n) {
    35             printf("0
    ");
    36             continue;
    37         }
    38         LL ans = Anm(n, k);
    39         LL temp = ans;
    40         for(LL i = k; i >= 2; --i) {
    41             temp /= i;
    42         }
    43         printf("%lld
    ", ans * temp);
    44     }
    45     return 0;
    46 }
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  • 原文地址:https://www.cnblogs.com/Recoder/p/5913273.html
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