463B - Caisa and Pylons - CodeForces Solution

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;

#define test_case int t;cin>>t;while(t--)
#define ll long long
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
//#define endl "\n"

/*
include <ext/pb_ds/assoc_container.hpp>
include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template<class T> using ordered_set = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
// less: it is the basic for comparison of two function. Use less_equal for ordered multiset.
// order_of_key(k): Number of items  strictly smaller than k
// find_by_order(k): kth element in a set (counting from zero)
*/

const double pi = acos(-1.0);
const double EPS = 1e-9;
const int mod = 1e9+7;

void Fast()
{
    std::ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
}
int gcd(ll a, ll b)
{
    return a ? gcd(b % a, a) : b;
}
ll lcm(ll a, ll b)
{
    return a / gcd(a, b) * b;
}
void solve()
{
    int N;
    cin>>N;
    vector<int>V(N);
    for (int I=0;I<N;I++)
    {
        cin>>V[I];
    }
    int E=0,cost=V[0];
    for (int I=0;I<N-1;I++)
    {
        if (V[I]-V[I+1]<0)
        {
            if (E>=abs(V[I]-V[I+1]))
            {
                E-=abs(V[I]-V[I+1]);
            }
            else
            {
                cost+=abs(V[I]-V[I+1])-E;
                E=0;
            }
        }
        else
        {
            E+=V[I]-V[I+1];
        }
    }
    cout<<cost<<endl;
}
int main()
{
    //freopen("hunter.in","r",stdin);
    //freopen(".out","w",stdout);
    Fast();
    //test_case
    solve();
    return 0;
}