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StockPairing.java
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StockPairing.java
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import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
public class StockPairing {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
int c[] = new int[n];
int pairs = 0;
for(int c_i=0; c_i < n; c_i++){
c[c_i] = in.nextInt();
}
HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
for(int i = 0; i < c.length; i++)
{
if(map.get(c[i]) != null)
{
int existing = map.get(c[i]);
map.put(c[i], ++existing);
}
else
{
map.put(c[i], 1);
}
}
for(Map.Entry<Integer, Integer> entry : map.entrySet())
{
int key = entry.getKey();
int val = entry.getValue();
if(val % 2 == 0)
{
pairs += (val / 2);
}
else
{
val = val - 1;
pairs += (val / 2);
}
}
System.out.println(pairs);
}
}