Rain Water Harvesting

#1

#include<bits/stdc++.h>
using namespace std;
int main() {
int a[1000];
int n;
cin>>n;

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

int l[1000];
int r[1000];

l[0]=a[0];
r[0]=a[0];
int water=0;

for(int i=1;i<n;i++){
	l[i]=max(l[i-1],a[i]);
}
r[n-1]=a[n-1];

for(int i=n-2;i>=0;i--){
	r[i]=max(r[i+1],a[i]);
}

for(int i=0;i<n;i++){
	water+=min(l[i],r[i])-a[i];
}
cout<<water<<endl;
return 0;

}

this code is running for some test cases only.where is my mistake

#2

got these issues:

  1. Take correct array sizes (as N=1000000 for some cases)
  2. Take long long as type to avoid any overflow.

min(l[i],r[i])-a[i] can be neagtive also!
do this way : long long x = min(l[i],r[i])-a[i];
if(x>0)
water+=x

#3

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