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Maximum_area_Histogram.cpp
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135 lines (130 loc) · 2.96 KB
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/*
written by Pankaj Kumar.
country:-INDIA
*/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll ;
typedef vector<ll> vl;
#define speed cin.tie(0);cout.tie(0);ios_base::sync_with_stdio(0);
// define values.
// #define mod 1000000007
#define phi 1.618
/* Abbrevations */
#define ff first
#define ss second
#define mp make_pair
#define line cout<<endl;
#define pb push_back
#define Endl "\n"
// loops
#define forin(arr,n) for(ll i=0;i<n;i++) cin>>arr[i];
// Some print
#define no cout<<"NO"<<endl;
#define yes cout<<"YES"<<endl;
#define cc ll test;cin>>test;while(test--)
// sort
#define all(V) (V).begin(),(V).end()
#define srt(V) sort(all(V))
#define srtGreat(V) sort(all(V),greater<ll>())
#define printv(v) for(ll i=0;i<ll(v.size());i++){cout<<v[i]<<" ";} line;
/* ONLINE JUDGE */
#ifdef ONLINE_JUDGE
freopen("input.txt", "r", stdin);freopen("output.txt", "w", stdout);
#endif
// function
ll power(ll x,ll y,ll mod)
{
ll res=1;
// x=x%mod;
while(y>0)
{
if(y%2==1)
{
res*=x;
// res=res%mod;
}
y/=2; x*=x; // x=x%mod;
}
return res;
}
// datatype definination
#define ordered_set tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>
/* ascii value
A=65,Z=90,a=97,z=122
*/
/* -----------------------------------------------------------------------------------*/
ll solve()
{
ll n;
cin>>n;
vl v(n,0);
for(ll i=0;i<n;i++)
cin>>v[i];
vl nsl,nsr;
ll maxo=0;
// for nsl
stack<pair<ll,ll>> st;
st.push({0,-1});
for(ll i=0;i<n;i++)
{
if(st.empty())
nsl.pb(-1);
else if(st.top().ff<v[i])
nsl.pb(st.top().ss);
else
{
while(st.size()>0&&st.top().ff>=v[i])
st.pop();
if(st.size()==0)
nsl.pb(-1);
else
nsl.pb(st.top().ss);
}
st.push({v[i],i});
}
// for nsr
stack<pair<ll,ll>> st1;
st1.push({0,n});
for(ll i=n-1;i>=0;i--)
{
if(st1.empty())
nsr.pb(-1);
else if(st1.top().ff<v[i])
nsr.pb(st1.top().ss);
else
{
while(st1.size()>0&&st1.top().ff>=v[i])
st1.pop();
if(st1.size()==0)
nsr.pb(-1);
else
nsr.pb(st1.top().ss);
}
st1.push({v[i],i});
}
reverse(all(nsr));
for(ll i=0;i<nsl.size();i++)
{
ll temp=abs(nsl[i]-nsr[i])-1;
temp*=v[i];
maxo=max(maxo,temp);
}
cout<<maxo<<endl;
return 0;
}
int main()
{
speed;
cout<<"Maximum area histogram."<<endl;
//freopen("input.txt"a, "r", stdin);
solve();
}
/* stuff you should look before submission
* int overflow
* special test case (n=0||n=1||n=2)
* don't get stuck on one approach if you get wrong answer
*/