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I’ve beern trying to solve this question but getting timeout for most test cases. Can anyone help me in optimising this?
Problem Statement :
You are given an array A of length N. You have to choose a subset S from given array A, such that average of S is less than K. You need to print the maximum possible length of S.
Input format :
The first line of each input contains N, length of array A. Next line contains N space separated elements of array A. Next line of input contains an integer Q, Number of queries. Each following Q lines contains a single integer K.
Output format :
For each query, print single integer denoting the maximum possible length of the subset.
Sample Input
5 1 2 3 4 5 5 1 2 3 4 5
Sample Output
0 2 4 5 5
Explanation
- In first query, there is no possible subset such that its average is less than 1.
- In second query, you can select the subset {1,2}.
- In third query, you can select the subset {1,2,3,4}.
- In fourth and fifth query, you can seelct the complete array {1,2,3,4,5}.
Here’s my solution:
import java.util.*;
public class Playground {
public static void main(String args[] ) throws Exception {
Scanner s = new Scanner(System.in);
long n = Long.parseLong(s.nextLine()); // Reading input from STDIN
String[] temp = s.nextLine().trim().split(" ");
long[] arr = new long[(int) n];
for (int i = 0; i < n; i++)
arr[i] = Integer.parseInt(temp[i]);
long q = Long.parseLong(s.nextLine());
long[] queries = new long[(int) q];
for (int i = 0; i < q; i++) {
long x = Long.parseLong(s.nextLine());
queries[i] = x;
}
PriorityQueue<Long> queue = new PriorityQueue<>();
for (long x : arr)
queue.add(x);
for (long x : queries) {
double avg = 0;
List<Long> list = new ArrayList<>();
int i = 0;
int sum = 0;
boolean flag = false;
while (! queue.isEmpty()) {
long num = queue.poll();
i++;
list.add(num);
sum += num;
avg = (double) sum / i;
if (avg >= x) {
System.out.println(i - 1);
flag = true;
break;
}
}
if (! flag)
System.out.println(n);
queue.addAll(list);
}
}
}
Answer
An easy way to solve this is to sort the array first.
After you sorted the array so each element is equal or greater than the last, then solving a single run is easy:
int count = 0;
int limit = 0;
for (int i : sortedArray) {
int diff = i - maxAvg;
if (limit + diff < 0) {
limit += diff;
count++
} else {
break;
}
}
System.out.println(count);
This works because if the difference to the max average is negative you can use values with a positive difference until you hit the limit.
Sorting the array is O(n*log(n)), and for each solution you only need O(n)
This is my full solution with all the parsing:
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int arrLen = Integer.parseInt(sc.nextLine());
int[] array = new int[arrLen];
String[] strNums = sc.nextLine().split(" ", arrLen);
for (int i = 0; i < arrLen; i++) {
array[i] = Integer.parseInt(strNums[i]);
}
Arrays.sort(array);
int numTests = Integer.parseInt(sc.nextLine());
for (int i = 0; i < numTests; i++) {
int maxAvg = Integer.parseInt(sc.nextLine());
int limit = 0;
int count = 0;
for (int j : array) {
int diff = j - maxAvg;
if (limit + diff < 0) {
count++;
limit += diff;
} else {
break;
}
}
System.out.println(count);
}
sc.close();
}