Can someone review my solution for this question and how can i optimise this solution
Given an array of n integers, you are required to create rectangles using pairs of integers from the array. Note that a particular integer can be used in at most one rectangle, and in order to create a rectangle, we must have exactly two pairs of integers with the same values. For example, you can create a rectangle using integers [2, 2, 5, 5] and [4, 4, 4, 4], but not with [3, 3, 5, 8]. The goal is to maximize the total sum of areas of all the rectangles formed.
To make the problem more interesting, you are allowed to reduce any integer by at most 1.
Given the array of integers, find the maximum sum of areas of rectangles that can be formed such that each element of the array can be used as length or breadth of at most one rectangle, and you are allowed to decrease any integer by at most 1.
import java.util.*;
public class RectangleAreaMax {
public static void main(String[] args) {
int r = maxSumArea(new int[]{1,1,2,2,3,3,4,5});
System.out.println(r); //14
int r1 = maxSumArea(new int[]{9,9,9,9,8,8,7,7,6,6,6,5,4});
System.out.println(r1); //167
int r2 = maxSumArea(new int[]{2,3,3,4,6,8,8,6});
System.out.println(r2); //54
}
public static int maxSumArea(int[] sideLengths){
int result = 0;
Map<Integer, Integer> freq = new TreeMap<>(Collections.reverseOrder());
Set<Integer> uniqueSide = new HashSet<>();
for(int side : sideLengths){
if(!uniqueSide.contains(side)){
uniqueSide.add(side);
}
freq.put(side, freq.getOrDefault(side, 0)+1);
}
Map<Integer, Integer> pairMap = new TreeMap<>(Collections.reverseOrder());
for(Map.Entry<Integer, Integer> entry : freq.entrySet()){
int sideNum = entry.getKey();
int sideFreq = entry.getValue();
if(sideFreq % 2 == 0){
pairMap.put(sideNum, sideFreq / 2);
}
else {
int qu = sideFreq / 2;
if(qu > 0) {
pairMap.put(sideNum, sideFreq / 2);
}
if(uniqueSide.contains(sideNum - 1)){
freq.put(sideNum - 1, freq.get(sideNum - 1) + 1);
}
}
}
List<Integer> rem = new ArrayList<>();
for(Map.Entry<Integer, Integer> entry : pairMap.entrySet()){
if(entry.getValue() % 2 != 0){
rem.add(entry.getKey());
if(entry.getValue() / 2 > 0){
result += Math.pow(entry.getKey(), entry.getValue()-1);
}
}
else {
result += Math.pow(entry.getKey(), entry.getValue());
}
}
for(int i = 0; i < rem.size(); i++){
result += rem.get(i) * rem.get(i+1);
i++;
}
return result;
}
}