题解 | #三个数的最大乘积#

import java.util.*;


public class Solution {
    /**
     * 最大乘积
     * @param A int整型一维数组 
     * @return long长整型
     */
    public long solve (int[] A) {
        // write code here
        long result = 0L;
        if(A.length == 3){
            result = A[0] * A[1] * A[2];
            return result;
        }
        ArrayList<Long> neg = new ArrayList<>();
        ArrayList<Long> pos = new ArrayList<>();

        long result1 = 0L;
        long result2 = 0L;

        for(int i = 0; i < A.length; i++){
            if(A[i] < 0){
                neg.add((long)A[i]);
            }
            else{
                pos.add((long)A[i]);
            }
        }
        Collections.sort(neg, new Comparator<Long>(){
            @Override
            public int compare(Long num1, Long num2){
                if(num1 > num2){
                    return 1;
                }
                else{
                    return -1;
                }
            }
        });
        Collections.sort(pos, new Comparator<Long>(){
            @Override
            public int compare(Long num1, Long num2){
                if(num1 > num2){
                    return 1;
                }
                else{
                    return -1;
                }
            }
        });
        if (neg.size() < 2){
            result = pos.get(pos.size() - 1) * pos.get(pos.size() - 2) * pos.get(pos.size() - 3);
            return result;
        }
        else if(pos.size() == 2){
            result = pos.get(pos.size() - 1) * neg.get(0) * neg.get(1);
            return result;
        }
        else if (pos.size() == 0) {
            result = neg.get(0) * neg.get(1) * neg.get(2);
            return result;
        }
        else{
            result1 = pos.get(pos.size() - 1) * pos.get(pos.size() - 2) * pos.get(pos.size() - 3);
            result2 = pos.get(pos.size() - 1) * neg.get(0) * neg.get(1);
            if((result1 - result2) >= 0){
                return result1;
            }
            else{
                return result2;
            }
        }
    }
}