Java: Find and print one continuous subarray to sort an entire array

Last update on April 01 2025 10:45:47 (UTC/GMT +8 hours)

Write a Java program to find and print one continuous subarray (from a given array of integers) that if you only sort the said subarray in ascending order then the entire array will be sorted in ascending order.

Example:
Input :
nums1 = {1, 2, 3, 0, 4, 6}
nums2 = { 1, 3, 2, 7, 5, 6, 4, 8}
Output:
Continuous subarray:
1 2 3 0
Continuous subarray:
3 2 7 5 6 4

Sample Solution:

Java Code:

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

// Define the 'solution' class.
public class solution {
  // Define a method to find the minimum continuous subarray for sorting.
  public static int[] findUnsortedSubarray(int[] nums) {
    // Initialize an array to store the result, where result[0] represents the start index and result[1] represents the end index.
    int[] result = new int[2];
    
    // Get the length of the input array.
    int n = nums.length;
    
    // Initialize variables for the start and end indices and for finding the minimum and maximum values.
    int start = -1;
    int end = -2;
    int min = nums[n - 1];
    int max = nums[0];
    
    // Traverse the array to find the subarray that needs sorting.
    for (int i = 1; i < n; i++) {
      // Update the maximum and minimum values.
      max = Math.max(max, nums[i]);
      min = Math.min(min, nums[n - 1 - i]);
      
      // Check if the current element is less than the maximum value.
      if (nums[i] < max) {
        end = i;
      }
      
      // Check if the current element is greater than the minimum value.
      if (nums[n - 1 - i] > min) {
        start = n - 1 - i;
      }
    }
    
    // Update the result array with the start and end indices of the subarray to be sorted.
    result[0] = start;
    result[1] = end;

    // Return the result.
    return result;
  }
    
  public static void main(String[] args)
  {
    // Initialize the first array.
    int[] nums1 = {1, 2, 3, 0, 4, 6};
    System.out.printf("\nOriginal array: "+Arrays.toString(nums1));	

    // Find and print the continuous subarray that needs sorting.
    int[] result1 = findUnsortedSubarray(nums1);
    System.out.printf("\nContinuous subarray:\n");
    for (int i = result1[0]; i <= result1[1]; i++) {
        System.out.print(nums1[i] + " ");
    }

    // Initialize the second array.
    int[] nums2 = { 1, 3, 2, 7, 5, 6, 4, 8};
    System.out.printf("\n\nOriginal array: "+Arrays.toString(nums2));	
    System.out.printf("\nContinuous subarray:\n"); 

    // Find and print the continuous subarray that needs sorting.
    int[] result2 = findUnsortedSubarray(nums2);
    
    for (int i = result2[0]; i <= result2[1]; i++) {
        System.out.print(nums2[i] + " ");
    }
  }  
}

Sample Output:

Original array: [1, 2, 3, 0, 4, 6]
Continuous subarray:
1 2 3 0 

Original array: [1, 3, 2, 7, 5, 6, 4, 8]
Continuous subarray:
3 2 7 5 6 4 

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to find the longest contiguous subarray that is already sorted.
• Write a Java program to find the number of elements that need to be sorted to make the whole array sorted.
• Write a Java program to find the smallest contiguous subarray that, when reversed, will make the entire array sorted.
• Write a Java program to check if an array can be sorted by swapping at most two elements.

Java Code Editor:

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