E. Buy Low Sell High
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
You can perfectly predict the price of a certain stock for the next N days. You would like to profit on this knowledge, but only want to transact one share of stock per day. That is, each day you will either buy one share, sell one share, or do nothing. Initially you own zero shares, and you cannot sell shares when you don't own any. At the end of the N days you would like to again own zero shares, but want to have as much money as possible.
Input
Input begins with an integer N (2 ≤ N ≤ 3·105), the number of days.
Following this is a line with exactly N integers p1, p2, ..., pN (1 ≤ pi ≤ 106). The price of one share of stock on the i-th day is given by pi.
Output
Print the maximum amount of money you can end up with at the end of N days.
Examples
input
Copy
9 10 5 4 7 9 12 6 2 10
output
Copy
20
input
Copy
20 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4
output
Copy
41
Note
In the first example, buy a share at 5, buy another at 4, sell one at 9 and another at 12. Then buy at 2 and sell at 10. The total profit is - 5 - 4 + 9 + 12 - 2 + 10 = 20.
#include<bits/stdc++.h>
using namespace std;
#define ll long long
priority_queue <int, vector <int>, greater<int> > q;
int main(){
int n;
scanf("%d", &n);
ll ans = 0;
for(int i = 0, x; i < n; i++){
scanf("%d", &x);
if(!q.empty() && q.top() < x) ans += (x - q.top()), q.pop(), q.push(x);
q.push(x);
}
printf("%lld\n", ans);
return 0;
}