Java: Find minimum subarray sum of specified size in a given array of integers

Last update on May 09 2025 12:51:22 (UTC/GMT +8 hours)

69. Find minimum subarray sum of specified size

Write a Java program to find the minimum subarray sum of specified size in a given array of integers.

Example:
Input :
nums = { 1, 2, 3, 4, 5, 6, 7, 8, 9,10}
Output:
Sub-array size: 4
Sub-array from 0 to 3 and sum is: 10

Sample Solution:

Java Code:

// Import the necessary Java classes.
import java.util.*;

// Define the 'solution' class.
class solution {
    // Method to find the subarray with the minimum sum of size 'k'.
    public static int[] find_min_subarray_sum(int[] nums, int k) {
        // Initialize variables to track the subarray sum and its minimum.
        int sub_arr_sum = 0;
        int min_sub_arr = Integer.MAX_VALUE;
        int last = 0;
        int[] result = new int[3]; // Store the result [start, end, min sum].

        // Iterate through the 'nums' array.
        for (int i = 0; i < nums.length; i++) {
            sub_arr_sum += nums[i];

            // Check if the subarray size 'k' is reached.
            if (i + 1 >= k) {
                // Update the minimum subarray sum and its endpoint.
                if (min_sub_arr > sub_arr_sum) {
                    min_sub_arr = sub_arr_sum;
                    last = i;
                }

                // Remove the contribution of the first element in the subarray.
                sub_arr_sum -= nums[i + 1 - k];
            }
        }

        // Store the results in the 'result' array.
        result[0] = last - k + 1; // Start index of the minimum subarray.
        result[1] = last; // End index of the minimum subarray.
        result[2] = min_sub_arr; // Minimum subarray sum.
        return result;
    }

    // Main method to demonstrate finding the minimum sum subarray.
    public static void main(String[] args) {
        // Initialize the 'nums' array and subarray size 'k'.
        int[] nums = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        int k = 4;

        // Print the original array and subarray size.
        System.out.printf("\nOriginal array: " + Arrays.toString(nums));
        System.out.printf("\nSub-array size: %d", k);

        // Find and print the minimum sum subarray.
        int[] result = find_min_subarray_sum(nums, k);
        System.out.printf("\nSub-array from %d to %d and sum is: %d", result[0], result[1], result[2]);
    }
}

Sample Output:

Original array: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Sub-array size: 4
Sub-array from 0 to 3 and sum is: 10

Flowchart:

Flowchart: Find minimum subarray sum of specified size in a given array of integers.

For more Practice: Solve these Related Problems:

Write a Java program to find the maximum subarray sum of a specified size.
Write a Java program to find the smallest subarray with a sum greater than a given value.
Write a Java program to find the subarray with the smallest sum where the number of elements is at least k.
Write a Java program to find the largest difference between the sum of two subarrays of equal size.

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