831A - Unimodal Array - CodeForces Solution

implementation *1000

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Python Code: 

n=int(input())
a=*map(int,input().split()),
l=0
r=n
while l+1<n and a[l]<a[l+1]:
    l+=1
while r>0 and a[r-2]>a[r-1]:
    r-=1
print('YNEOS'[len({*a[l:r]})!=1::2])

C++ Code: 

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; i++)
    {
        cin >> a[i];
    }
    int inc = 1, c = 0, d = 0;
    for (int i = 1; i < n; i++)
    {
        if (a[i] > a[i - 1])
        {
            if (c == 1 || d == 1)
            {
                cout << "NO" << endl;
                return 0;
            }
        }
        else if (a[i] == a[i - 1])
        {
            if (d == 1)
            {
                cout << "NO" << endl;
                return 0;
            }
            c = 1;
        }
        else
        {
            d = 1;
        }
    }
    cout << "YES" << endl;
    return 0;
}


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