#51nod 1305 Pairwise Sum and Divide
来源:互联网 发布:二阶矩阵 编辑:程序博客网 时间:2024/06/05 15:33
51nod 1305 Pairwise Sum and Divide
链接:http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1305
1305 Pairwise Sum and Divide
题目来源: HackerRank
基准时间限制:1 秒 空间限制:131072 KB 分值: 5 难度:1级算法题 收藏 取消关注
有这样一段程序,fun会对整数数组A进行求值,其中Floor表示向下取整:
fun(A)
sum = 0
for i = 1 to A.length
for j = i+1 to A.length
sum = sum + Floor((A[i]+A[j])/(A[i]*A[j]))
return sum
给出数组A,由你来计算fun(A)的结果。例如:A = {1, 4, 1},fun(A) = [5/4] + [2/1] + [5/4] = 1 + 2 + 1 = 4。
Input
第1行:1个数N,表示数组A的长度(1 <= N <= 100000)。
第2 - N + 1行:每行1个数A[i](1 <= A[i] <= 10^9)。
Output
输出fun(A)的计算结果。
Input示例
3
1 4 1
Output示例
4
.
思路(题解):
题意:即Ai中所以元素两两进行Floor((A[i]+A[j])/(A[i]*A[j]))的和;
题解:
化简Floor((A[i]+A[j])/(A[i]*A[j]))–>FLoor(1/A[i]+1/A[j])
由于FLoor为向下取整,则当(1/A[i]+1/A[j])<1时,FLoor结果为0,
对于任意A[i],A[i]为整数,且1 <= A[i] <= 10^9,
A[i]为整数,那很显然:
A[i]=1,1/A[i]=1
A[i]=2, 1/A[i]=0.5
A[i]=3, 1/A[i]=1/3
A[i]=4, 1/A[i]=0.25
以上得出结论:其实FLoor值只有两种情况,2(1+1)
或1(0.5+0.5或1+0)
不考虑Ai,Aj的位置的值组成情况
2: A[i]=1,A[j]=1
1: A[i]=1,A[j]>2或A[i]=2,A[j]=2
输入A[i]时,分别对A[i]=1,A[i]=2及A[i]>2进行计数,假设分别为a,b,c
sum=a*(b+c)+(1+a-1)(a-1)/2*2+(1+n-1)(n-1)/2*1
代码
#include<cstdio>#include<iostream>using namespace std;int main(){ int n; int y[4];y[2]=0;y[3]=0;int c=0; cin>>n; for(int i=1;i<=n;i++){ int x; cin>>x; if(x==1||x==2) y[x]++; else c++; } long long sum=0; sum+=(y[2]+c)*y[1]+y[1]*(y[1]-1); sum+=y[2]*(y[2]-1)/2;printf("%I64d\n",sum); }
不管水不水,开始记录到csdn里了
- 51nod 1305:Pairwise Sum and Divide
- 51NOD 1305 Pairwise Sum and Divide
- 51nod 1305 Pairwise Sum and Divide
- 51nod 1305 Pairwise Sum and Divide
- #51nod 1305 Pairwise Sum and Divide
- 51nod 1305 Pairwise Sum and Divide
- 51nod-【1305 Pairwise Sum and Divide】
- 51nod 1305 Pairwise Sum and Divide
- 51nod 1305 Pairwise Sum and Divide
- 51NOD 1305 Pairwise Sum and Divide
- 51nod - 1305 Pairwise Sum and Divide
- 51nod 1305 Pairwise Sum and Divide
- 【51Nod】1305 Pairwise Sum and Divide
- 51NOD 1305 Pairwise Sum and Divide
- 51nod 1305 Pairwise Sum and Divide
- 51Nod 1305Pairwise Sum and Divide
- 51Nod-1305 Pairwise Sum and Divide
- 51Nod 1305 Pairwise Sum and Divide
- 工作中积累的优秀博客
- windows安装服务程序
- pragma once
- Windows NT驱动
- error RC2104 : undefined keyword or key name: Select 1394
- #51nod 1305 Pairwise Sum and Divide
- 修改Makefile.am,无法生效
- iOS中常见的第三方登录
- hadoop-2.7.1/tmp/dfs/namesecondary/in_use.lock (Permission denied) 错误解决
- SwipeRefreshLayout基本使用和冲突解决机制
- 一个循环队列在linux下的应用
- TortoiseSVN 修改服务器地址url
- ubuntu 左边菜单栏不见
- Codeforces Intel Code Challenge Elimination Round(Oct/01/2016)