RainWater Trapping problem

#1

#include
#include<bits/stdc++.h>
#include<math.h>
using namespace std;
int main() {

int i,n,sum=0;
cin>>n;

int arr[n],arr1[n],arr2[n];

for(i=0;i<n;i++)
{
	cin>>arr[i];
}
arr1[n]=arr[0];

for(i=0;i<n;i++)
{
 	arr1[i]=max(arr1[i-1],arr[i]);
}
 arr2[n-1]=arr[n-1];
for(i=n-2;i>=0;i--)
{
	arr2[i]=max(arr2[i+1],arr[i]);
}

for(i=0;i<n;i++)
{
	sum+=min(arr1[i],arr2[i])-arr[i];
}

cout<<sum;
return 0;

}

tell the problem

#2

@arsh_goyal at line 16 of your code arr1[0] should be equal to arr[0] and start your for loop from i=1.

#3

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