2017 ECL-FINAL J.Straight Master

Posted 2021-01-18 wangcwcgnaw

 

题目链接：http://codeforces.com/gym/101775/problem/J

 

思路：序列差分一下，然后用得到的查分序列乱搞就可以了

           注意差分序列第一项等于a[i]，之后n-1项为cha[i]=a[i]-a[i-1]，第n+1项为0-a[n]

 

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 
 4 typedef long long ll;
 5 const int mod=1e9+7;
 6 const int maxn=2e5+10;
 7 const int inf=0x3f3f3f3f;
 8 const double eps=1e-14;
 9 const double pi=acos(-1.0);
10 #define mem(s,v) memset(s,v,sizeof(s))
11 #define pdd pair<double,double>
12 #define pii pair<int,int>
13 
14 int t,n;
15 int a[maxn],cha[maxn];
16 
17 int main(){
18     scanf("%d",&t);
19     for(int k=1;k<=t;++k){
20         scanf("%d",&n);
21         for(int i=1;i<=n;++i){
22             scanf("%d",&a[i]);
23             if(i==1) cha[i]=a[i];
24             else cha[i]=a[i]-a[i-1];
25         }
26         cha[n+1]=0-a[n];
27         int sum=0;
28         int flag=1;
29         if(cha[2]<0||cha[3]<0) flag=0;
30         for(int i=1;i<=n+1;++i){
31 //            cout<<cha[i]<<" ";
32             if(cha[i]>=0) sum+=cha[i];
33             int temp=i+3;
34             if(temp>n+1) break;
35             if(cha[temp]<0) sum+=cha[temp];
36             if(sum<0) break;
37         }
38 //        cout<<endl;
39         if(sum) flag=0;
40         printf("Case #%d: ",k);
41         if(flag) printf("Yes
");
42         else printf("No
");
43     }
44     return 0;
45 }