# Zoj 3672 thinking questions

Source: Internet
Author: User

Http://acm.zju.edu.cn/onlinejudge/showProblem.do? Problemid = 4915

I am so old that my mind will not be moved, but even if I have searched question a, I still haven't figured out my way of thinking.

Three points:

1. segma (A [I]-B [I]) must be an even number, because each operation is equivalent to minus 2 * Delta

2. A [I]> = B [I] The question is clearly stated and can only be subtracted. Therefore, this must satisfy

I thought of the first two points, but I could give a counterexample. Then my teammate a fell.

3. Max (A [I]-B [I]) * 2 <= segma (A [I]-B [I]). Otherwise, the maximum value will definitely not be deleted.

But I still haven't summed up my thinking methods. I have been doing this all the time. I have enumerated the examples from an early age, searched for methods, and then promoted them to a large one, but it seems that I can't do it this time.

You may need to summarize the rules from the counterexamples. If you want to solve the problem, you should be right.

`#include <cstdio>#include <cstring>#include <algorithm>#include <string>#include <iostream>#include <iomanip>#include <cmath>#include <map>#include <set>#include <queue>using namespace std;#define ls(rt) rt*2#define rs(rt) rt*2+1#define ll long long#define ull unsigned long long#define rep(i,s,e) for(int i=s;i<e;i++)#define repe(i,s,e) for(int i=s;i<=e;i++)#define CL(a,b) memset(a,b,sizeof(a))#define IN(s) freopen(s,"r",stdin)#define OUT(s) freopen(s,"w",stdout)const ll ll_INF = ((ull)(-1))>>1;const double EPS = 1e-8;const int INF = 100000000;const int MAXN = 10000+100;ll a[MAXN],b[MAXN];ll vis[MAXN];int n;int main(){    while(~scanf("%d",&n))    {        CL(vis,0);        int flag=1;        ll mmax=0,ret=0;        for(int i=0;i<n;i++)        {            scanf("%lld%lld",&a[i],&b[i]);            if(a[i]<b[i])flag=0;            if(a[i]>=b[i])vis[i]=a[i]-b[i];            mmax=max(vis[i],mmax);            ret+=vis[i];        }        if(flag==0 || 2*mmax >ret || ret%2)            printf("NO\n");        else            printf("YES\n");    }    return 0;}`

Zoj 3672 thinking questions

Related Keywords:

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

## A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

• #### Sales Support

1 on 1 presale consultation

• #### After-Sales Support

24/7 Technical Support 6 Free Tickets per Quarter Faster Response

• Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.