题目链接
1 /*
2 Name:
3 Copyright:
4 Author:
5 Date: 2018/5/6 19:34:23
6 Description:
7 */
8 #include <iostream>
9 #include <cstdio>
10 #include <cstring>
11 using namespace std;
12 int arr[1005];
13 int main()
14 {
15 int n;
16 while (cin>>n) {
17 for (int i=0; i<n; i++) {
18 cin>>arr[i];
19 }
20 if (n == 1) {//1
21 cout<<"YES"<<endl;
22 continue;
23 }
24 int flag = 1;
25 for (int i=0; i<n; i++) {
26 if (arr[i] != arr[i-1]) flag = 0;
27 }
28 if (flag == 1) {//全相等
29 cout<<"YES"<<endl;
30 continue;
31 }
32
33 bool destory = false;
34 if (arr[0] == arr[1]) {
35 int tmp = arr[0];
36 int i = 2;
37 while (arr[i] == arr[i-1]) i++;
38 //不相等
39 for (; i<n; i++) {
40 if (arr[i] >= arr[i-1]) {
41 destory = true;
42 break;
43 } else {
44 }
45 }
46 //判断完毕
47 if (destory) {
48 cout<<"NO"<<endl;
49 } else{
50 cout<<"YES"<<endl;
51 }
52 } else {
53 int i=1;
54 //递增
55 while (arr[i] > arr[i-1] && i<n) i++;
56 //相等
57 while (arr[i] == arr[i-1] && i<n) i++;
58 //递减
59 while (arr[i] < arr[i-1] && i<n) i++;
60 if (i == n) {
61 cout<<"YES"<<endl;
62 } else {
63 cout<<"NO"<<endl;
64 }
65 }
66 }
67 return 0;
68 }
