CodeForces-831A-Unimodal Array (水题)

题目链接

 /*
     Name:
     Copyright:
     Author:
     Date: 2018/5/6 19:34:23
     Description:
 */
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 using namespace std;
 int arr[];
 int main()
 {
     int n;
     while (cin>>n) {
         for (int i=; i<n; i++) {
             cin>>arr[i];
         }
         if (n == ) {//
             cout<<"YES"<<endl;
             continue;
         }
         int flag = ;
         for (int i=; i<n; i++) {
             if (arr[i] != arr[i-]) flag = ;
         }
         if (flag == ) {//全相等
             cout<<"YES"<<endl;
             continue;
         }

         bool destory = false;
         if (arr[] == arr[]) {
             int tmp = arr[];
             int i = ;
             while (arr[i] == arr[i-]) i++;
             //不相等
             for (; i<n; i++) {
                 if (arr[i] >= arr[i-]) {
                     destory = true;
                     break;
                 } else {
                 }
             }
             //判断完毕
             if (destory)  {
                 cout<<"NO"<<endl;
             } else{
                 cout<<"YES"<<endl;
             }
         } else {
             int i=;
             //递增
             while (arr[i] > arr[i-] && i<n) i++;
             //相等
             while (arr[i] == arr[i-] && i<n) i++;
             //递减
             while (arr[i] < arr[i-] && i<n) i++;
             if (i == n) {
                 cout<<"YES"<<endl;
             } else {
                 cout<<"NO"<<endl;
             }
         }
     }
     return ;
 }