Problem 702A — Maximum Increase | What is wrong in this Plz HELP I SPENT 2 Days finding bug PLZZZZ HELP.

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ABhinav2003's blog

Problem 702A — Maximum Increase | What is wrong in this Plz HELP I SPENT 2 Days finding bug PLZZZZ HELP.

By ABhinav2003, history, 6 years ago, In English

#include<bits/stdc++.h>
using namespace std;
int in=0 , ex;
int sub(int a[] , int len)
{
//	if(len<1)
//		return 0;
	 if(len <= 0  )
		return 0;

	  ex = sub(a,len-1);
	  cout<<"EX "<<ex<<"\n";

	 if(a[len-1] >a[len-2])
	 {
		int t = a[len-1]>a[len-2];cout<<"T "<<t<<"\n";
	 	 in = 1+sub(a,len-1);
	 }
	 cout<<"IN "<<in<<"\n";

	int max1 = max(in,ex);
	cout<<"MAX "<<max1<<"\n";

	return max1;
}

int main()
{
	int len;
	cin>>len;
	 int a[len];
	for(int i = 0;i<=len-1;i++)
	{
		cin>>a[i];
	}
	int m = sub(a , len);
	cout<<m;
}
[**HERE IS THE PROBLEM**](https://codeforces.me/problemset/problem/702/A)

ABhinav2003
6 years ago
8

Comments (4)

Show archived | Write comment?

shinigami_orz

6 years ago, hide # |

There are many flaws in this code.

Base case is len <= 0 so, when len = 1, the index of a[len-2] will become negative.
in is a global variable, you'll have to add in = 0 before the if statement.

Even if you correct these flaws, the basic flaw is that this method will give you a subsequence instead of a subarray.

For example, for the input 1 2 3 10 4 5 6, your output will be 6 (after correcting the mentioned 2 points).

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ABhinav2003

6 years ago, hide # ^ |

PLZ CAN U CORRECT MY FLAW AND GIVE IT TO ME I CAN"T UNDERSTAND IT PROPERLY BRO PLZ HELP I AM struggling for about 2-3 days now and not able to do this

actually i have just started DP PLZ UNDERSTAND AND HELP ME JUST REWRITE THE FUNCTION WITH REMOVING ALL FLAWS

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spookywooky

6 years ago, hide # ^ |

+12

https://www.wikihow.com/Turn-Off-Caps-Lock

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shinigami_orz

6 years ago, hide # ^ |

Recursive code which will give TLE

#include<bits/stdc++.h>
#define M 100005
using namespace std;

int sub(int a[], int len)
{
	if(len <= 1) return 1;
	if(a[len-1] > a[len-2]) return sub(a, len-1) + 1;
	else return 1;
}

int main()
{
	int len;
	cin>>len;
	int a[len], ans = 0;
	for(int i=0; i<=len-1; i++)
	{
		cin>>a[i];
	}
	for(int i=0; i<=len-1; i++)
	{
		ans = max(ans, sub(a, i+1));
	}
	cout<<ans;
}

Memoized version of the same code

#include<bits/stdc++.h>
#define M 100005
using namespace std;

int dp[M];

int sub(int a[], int len)
{
	if(len <= 1) return 1;
	if(dp[len] != -1) return dp[len];
	if(a[len-1] > a[len-2]) return dp[len] = sub(a, len-1) + 1;
	else return dp[len] = 1;
}

int main()
{
	memset(dp, -1, sizeof dp);
	int len;
	cin>>len;
	int a[len], ans = 0;
	for(int i=0; i<=len-1; i++)
	{
		cin>>a[i];
	}
	for(int i=0; i<=len-1; i++)
	{
		ans = max(ans, sub(a, i+1));
	}
	cout<<ans;
}

No dp required

#include<bits/stdc++.h>
using namespace std;

int main()
{
	int n;
	cin>>n;
	int a[n], ans = 0, mx = 1;
	for(int i=0; i<n; i++) cin>>a[i];
	for(int i=1; i<n; i++)
	{
		if(a[i] <= a[i-1]) ans = max(ans, mx), mx = 1;
		else mx++;
	}
	ans = max(ans, mx);
	cout<<ans;
}

I'd strictly recommend you to learn dp first or you might not understand my solution.

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