Maximum Length Bitonic Subarray

#1

Here is my code. I cannot seem to find an error in this. Please rectify and also tell a test case for which it fails. TIA

#include
#include<bits/stdc++.h>
using namespace std;
int main() {
int t,n;
cin >> t;
while(t–){
cin >> n;
int a[n];

	for(int i = 0 ; i < n ; i++){
		cin >> a[i];
	}

	int len = 1, i = 1,maxlen=0;
	while( i < n ){
	    len = 1;
		while(a[i-1] < a[i] && i < n){
			len++;
			i++;
		}
		while(a[i-1] > a[i] && i < n){
			len++;
			i++;
		}
		maxlen = max(len,maxlen);
	}
	cout << maxlen << endl;
}
return 0;

}

#2

check ur first while statement
this is the error in ur code
u have to write while(t–)

2nd check for the test case
15
5 4 3 4 5 4 3 2 1 2 3 4 5 6 2

#3

What are you saying about the while statement. Please clarify.
I have tried the test-case. Answer for the test-case is 7.

#4

but ans is 10
5 4 3 2 1 2 3 4 5 6
first decreasing then in creasing.

#5

oh! i did not realize it could be decreasing first and then increasing. I thought only increasing, only decreasing OR increasing and then decreasing. Thanks. I’ll change accordingly.

#6

if ur doubt got resolved mark it r3solved

#7

but according to question i.e subarray is first increasing and then decreasing or entirely increasing or decreasing. i am getting same answer 7

#8

I used two arrays, inc[n] and dec[n] to solve this problem.
My code gives correct and in all the test cases I applied it to but the CB compiler gives output wrong answer. Can you please tell me the mistake I have made.
My code:-

#include <bits/stdc++.h>
using namespace std;
int main() {
    int testcases;
    cin>>testcases;
    for(int t=0;t<testcases;t++){
        int n;
        cin>>n;
        int a[n];
        for(int i=0;i<n;i++){
            cin>>a[i];
        }
        int inc[n];
        int dec[n];
        inc[0]=0;
        dec[n-1]=0;
        for(int i=1;i<n;i++){
            if(a[i]>a[i-1]){
                inc[i]=inc[i-1]+1;
            }
            else{
                inc[i]=0;
            }
        }
        for(int k=n-2;k>=0;k--){
            if(a[k]>a[k+1]){
                dec[k]=dec[k+1]+1;
            }
            else{
                dec[k]=0;
            }
        }
        int inc1[n];
        int dec1[n];
        dec1[0]=0;
        inc1[n-1]=0;
        for(int i=1;i<n;i++){
            if(a[i]<a[i-1]){
                dec1[i]=dec1[i-1]+1;
            }
            else{
                dec1[i]=0;
            }
        }
        for(int k=n-2;k>=0;k--){
            if(a[k]<a[k+1]){
                inc1[k]=inc1[k+1]+1;
            }
            else{
                inc1[k]=0;
            }
        }
        // cout<<"inc ";
        // for(int i=0;i<n;i++){
        //     cout<<inc[i]<<" ";
        // }
        // cout<<endl;
        // cout<<"dec ";
        // for(int i=0;i<n;i++){
        //     cout<<dec[i]<<" ";
        // }
        // cout<<endl;
        // cout<<"dec1 ";
        // for(int i=0;i<n;i++){
        //     cout<<dec1[i]<<" ";
        // }
        // cout<<endl;
        // cout<<"inc1 ";
        // for(int i=0;i<n;i++){
        //     cout<<inc1[i]<<" ";
        // }
        // cout<<endl;
        int ans=0;
        for(int i=0;i<n;i++){
            ans=max(ans,max((inc[i]+dec[i]),(inc1[i]+dec1[i])));
        }
        cout<<ans+1<<endl;
    }
}