CodeForces 609B The Best Gift
来源:互联网 发布:php 取字符串后几位 编辑:程序博客网 时间:2024/05/17 08:34
Description
Emily's birthday is next week and Jack has decided to buy a present for her. He knows she loves books so he goes to the local bookshop, where there are n books on sale from one of m genres.
In the bookshop, Jack decides to buy two books of different genres.
Based on the genre of books on sale in the shop, find the number of options available to Jack for choosing two books of different genres for Emily. Options are considered different if they differ in at least one book.
The books are given by indices of their genres. The genres are numbered from 1 to m.
Input
The first line contains two positive integers n and m (2 ≤ n ≤ 2·105, 2 ≤ m ≤ 10) — the number of books in the bookstore and the number of genres.
The second line contains a sequence a1, a2, ..., an, where ai (1 ≤ ai ≤ m) equals the genre of the i-th book.
It is guaranteed that for each genre there is at least one book of that genre.
Output
Print the only integer — the number of ways in which Jack can choose books.
It is guaranteed that the answer doesn't exceed the value 2·109.
Sample Input
4 32 1 3 1
5
7 44 2 3 1 2 4 3
18
Hint
The answer to the first test sample equals 5 as Sasha can choose:
- the first and second books,
- the first and third books,
- the first and fourth books,
- the second and third books,
- the third and fourth books.
- 题意:给出几种不同类的书,从中选两种不同类的书,问有多少种不同的方法。
- 刚开始弄错题意了,给出的N个数是,每本书的分类号。
#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;__int64 n,m,i,j,k,sum,num,a[15];int main(){while(scanf("%I64d%I64d",&n,&m)!=EOF){memset(a,0,sizeof(a));num=0;for(i=0;i<n;i++){scanf("%I64d",&k);a[k]++;}for(i=0;i<=11;i++){num+=a[i]*(n-a[i]);}printf("%I64d\n",num/2);}return 0;}
- Codeforces 609B The Best Gift 【水题】
- CodeForces 609B The Best Gift
- CodeForces 609B.The Best Gift
- CodeForces 609B The Best Gift
- CodeForces 609B The Best Gift
- ♥CodeForces 609B-B. The Best Gift【组合数学】
- 【CodeForces】609B - The Best Gift(水)
- CodeForces 609 B. The Best Gift(水~)
- CF 609B The Best Gift
- Educational Codeforces Round 3 B. The Best Gift
- Educational Codeforces Round 3 B.The Best Gift (数学)
- CodeForcess--609B--The Best Gift(模拟水题)
- Codeforces Educational Codeforces Round 3 B. The Best Gift(签到)
- CodeForces 609B The Best Giftgomg
- The best gift
- The Best Gift
- The Best Gift
- codeforces_609B. The Best Gift
- Bitcoin 的基本原理
- 2016年第二季度总结
- 滑动固定表格头和列--js,html,css--移动端--基于Iscroll
- 无限循环ScrollView
- ImageView的scaletype属性
- CodeForces 609B The Best Gift
- Spark知识体系完整解读
- linux的mysql的
- Codeforces 414b Mashmokh and ACM
- css选择器优先级
- TOMCAT8重启一闪而过
- Android知识点深究
- 新浪微博Oauth2.0授权认证及SDK、API的使用(Android)
- Git 本地的撤销修改和删除操作