HackerRank Java Subarray

문제 링크 : https://www.hackerrank.com/challenges/java-negative-subarray/problem

We define the following:

• A subarray of an -element array is an array composed from a contiguous block of the original array's elements. For example, if , then the subarrays are , , , , , and . Something like  would notbe a subarray as it's not a contiguous subsection of the original array.
• The sum of an array is the total sum of its elements.
  • An array's sum is negative if the total sum of its elements is negative.
  • An array's sum is positive if the total sum of its elements is positive.

Given an array of  integers, find and print its number of negative subarrays on a new line.

Input Format

The first line contains a single integer, , denoting the length of array .
The second line contains  space-separated integers describing each respective element, , in array . 

Constraints

Output Format

Print the number of subarrays of  having negative sums.

sample input

5

1 -2 4 -5 1

sample output

9

Explanation

There are nine negative subarrays of :

Thus, we print  on a new line.

간단하게,  연결되는 모든 subarray의 합을 검사하고 합이 음수인 경우 카운트해준다.

[1] = 1

[1,-2] = -1

[1,-2,4] = 3

[1,-2,4,-5] = -2

[1,-2,4,-5,1] = -1

[-2] = -2

[-2,4] = 2

[-2,4,-5] = -3

[-2,4,-5,1] = -2

[4] = 4

[4, -5] = -1

[4, -5, 1] = 0

[-5] = -5

[-5, 1] = -4

이런 식으로 모두 검사한다.

import java.util.*;

public class Solution {

    private static int subArrCnt = 0;

    private static ArrayList<Integer> subArr = new ArrayList<>();

    public static void main(String[] args) {

        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */

        Scanner scn = new Scanner(System.in);

        int elementsCount = scn.nextInt();

        int[] arr = new int[elementsCount];

        for (int i = 0; i < elementsCount; i++) {

            arr[i] = scn.nextInt();

        }

        scn.close();

        for ( int a = 0; a < arr.length; a++ ) {

            for (int i = 0; i < arr.length; i++) {

                for (int j = a; j <= i; j++) {

                    subArr.add(arr[j]);

                }

                int sum = 0;

                if (subArr.size() > 0) {

                    for (int t : subArr) {

                        sum += t;

                    }

                    if ( sum < 0 )

                        subArrCnt++;

                }

                subArr.clear();

            }

        }

    }

}