zoukankan      html  css  js  c++  java
  • Margarite and the best present

    Little girl Margarita is a big fan of competitive programming. She especially loves problems about arrays and queries on them.

    Recently, she was presented with an array aa of the size of 109109 elements that is filled as follows:

    • a1=−1
    • a2=2
    • a3=−3
    • a4=4
    • a5=−5
    • And so on ...

    That is, the value of the ii-th element of the array aa is calculated using the formula ai=i⋅(−1)iai=i⋅(−1)i.

    She immediately came up with qq queries on this array. Each query is described with two numbers: ll and rr. The answer to a query is the sum of all the elements of the array at positions from ll to rr inclusive.

    Margarita really wants to know the answer to each of the requests. She doesn't want to count all this manually, but unfortunately, she couldn't write the program that solves the problem either. She has turned to you — the best programmer.

    Help her find the answers!

    Input

    The first line contains a single integer qq (1≤q≤1031≤q≤103) — the number of the queries.

    Each of the next qq lines contains two integers ll and rr (1≤l≤r≤1091≤l≤r≤109) — the descriptions of the queries.

    Output

    Print qq lines, each containing one number — the answer to the query.

    Example

    input

    Copy

    5
    1 3
    2 5
    5 5
    4 4
    2 3
    

    output

    Copy

    -2
    -2
    -5
    4
    -1
    

    Note

    In the first query, you need to find the sum of the elements of the array from position 11 to position 33. The sum is equal to a1+a2+a3=−1+2−3=−2a1+a2+a3=−1+2−3=−2.

    In the second query, you need to find the sum of the elements of the array from position 22 to position 55. The sum is equal to a2+a3+a4+a5=2−3+4−5=−2a2+a3+a4+a5=2−3+4−5=−2.

    In the third query, you need to find the sum of the elements of the array from position 55 to position 55. The sum is equal to a5=−5a5=−5.

    In the fourth query, you need to find the sum of the elements of the array from position 44 to position 44. The sum is equal to a4=4a4=4.

    In the fifth query, you need to find the sum of the elements of the array from position 22 to position 33. The sum is equal to a2+a3=2−3=−1a2+a3=2−3=−1.

    题解:对于多种情况考虑分析即可

    #include<cstdio>
    #include<algorithm>
    #include<cstring>
    #include<iostream>
    using namespace std;
    
    int main()
    {
    	int n;
    	cin>>n;
    
    	for(int t=0;t<n;t++)
    	{
    		int a,b;
    		long long int sum;
    		scanf("%d%d",&a,&b);
    		if(a%2==1&&b%2==1)
    		{
    			sum=-1*((a-b)/2+b);
    		}
    		else if(a%2==1&&b%2==0)
    		{
    			sum=(b-a+1)/2;
    		}
    		else if(a%2==0&&b%2==1)
    		{
    			sum=-1*(b-a+1)/2;
    		}
    		else
    		{
    			sum=(a-b)/2+b;
    		}
    		printf("%lld
    ",sum);
    		
    	}
    	return 0;
     } 
  • 相关阅读:
    SQL Server的AlwaysOn错误19456和41158
    kvm上的Linux虚拟机使用virtio磁盘
    利用HAProxy代理SQL Server的AlwaysOn辅助副本
    KVM安装部署
    ola.hallengren的SQL Server维护脚本
    在单链表的第i个位置后插入一个节点(阿里+腾讯等面试题总结)
    怎么发现RAC环境中&#39;library cache pin&#39;等待事件的堵塞者(Blocker)?
    php unserialize 返回false的解决方法
    千万别让这些举动断送了你的职业前程-好文共分享
    Android开发:仿美团下拉列表菜单,帮助类,复用简单
  • 原文地址:https://www.cnblogs.com/Staceyacm/p/10782087.html
Copyright © 2011-2022 走看看