Codeforces Round #424 A

Unimodal Array

题意：给一个数列，问是不是先递增后不变再递减的一部分

思路：xjb写

AC代码：

#include "iostream"
#include "string.h"
#include "stack"
#include "queue"
#include "string"
#include "vector"
#include "set"
#include "map"
#include "algorithm"
#include "stdio.h"
#include "math.h"
#define ll long long
#define bug(x) cout<<x<<" "<<"UUUUU"<<endl;
#define mem(a) memset(a,0,sizeof(a))
#define mp(x,y) make_pair(x,y)
using namespace std;
const long long INF = 1e18+1LL;
const int inf = 1e9+1e8;
const int N=1e5+100;

int n,a[105];
int main(){
    ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    cin>>n;
    for(int i=1; i<=n; ++i){
        cin>>a[i];
    }
    a[0]=0,a[n+1]=0;
    int p=0;
    for(int i=1; i<=n+1; ++i){
        if(a[i]<a[i-1]){
            p=i;
            break;
        }
    }
    int flag=1;
    for(int i=p+1; i<=n+1; ++i){
        if(a[i]>=a[i-1]){
            flag=0;
            break;
        }
    }
    p=n;
    for(int i=1; i<=n+1; ++i){
        if(a[i]==a[i-1]){
            p=i;
            break;
        }
    }
    for(int i=p+1; i<=n; ++i){
        if(a[i]>a[i-1]){
            flag=0;
            break;
        }
    }
    if(flag) cout<<"YES";
    else cout<<"NO";
    return 0;
}