Java: Consecutive Numbers in an array

Last update on May 09 2025 12:51:19 (UTC/GMT +8 hours)

76. Check if numbers in array can form a consecutive list

Write a Java program to determine whether numbers in an array can be rearranged so that each number appears exactly once in a consecutive list of numbers. Return true otherwise false.

Sample Data:
{1, 2 ,5, 0, 4, 3, 6} -> true
{1, 2 ,5, 0, 3, 6, 7} ->false

Pictorial Presentation:

Java Array Exercises: Consecutive Numbers in an array

Sample Solution-1:

Java Code:

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

// Define the 'Main' class.
public class Main {
  // Define the main method for running the program.
  public static void main(String[] args) {
    // Initialize an array of numbers.
    int[] nums = {1, 2 ,5, 0, 4, 3, 6};
    // int[] nums = {1, 2 ,5, 0, 3, 6, 7};
    System.out.printf("\nOriginal array: " + Arrays.toString(nums));

    // Call the 'test' method to check for consecutive numbers in the array.
    boolean result = test(nums);
    System.out.printf("\nCheck consecutive numbers in the said array! " + result);
  }

  // Define the 'test' method to check for consecutive numbers in the array.
  public static boolean test(int[] nums) {
    // Sort the 'nums' array in ascending order.
    Arrays.sort(nums);
    for (int i = 0; i < nums.length - 1; i++) {
      // Check if the current number and the next number are consecutive.
      if (nums[i] + 1 != nums[i + 1])
        return false;
    }
    return true;
  }
}

Sample Output:

Original array: [1, 2, 5, 0, 4, 3, 6]
Check consecutive numbers in the said array!true

Flowchart:

Flowchart: Consecutive Numbers in an array.

Sample Solution-2:

Java Code:

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

// Define the 'Main' class.
public class Main {
  // Define the main method for running the program.
  public static void main(String[] args) {
    // Initialize an array of numbers.
    int[] nums = {1, 2 ,5, 0, 3, 6, 7};
    // int[] nums = {1, 2 ,5, 0, 4, 3, 6};
    System.out.printf("\nOriginal array: " + Arrays.toString(nums));

    // Call the 'test' method to check for consecutive numbers in the array.
    boolean result = test(nums);
    System.out.printf("\nCheck consecutive numbers in the said array! " + result);
  }

  // Define the 'test' method to check for consecutive numbers in the array.
  public static boolean test(int[] nums) {
    // Sort the 'nums' array in ascending order.
    Arrays.sort(nums);
    // Check if the last number in the sorted array is equal to the first number plus the array length minus 1.
    return nums[nums.length - 1] == (nums[0] + nums.length - 1);
  }
}

Sample Output:

Original array: [1, 2, 5, 0, 3, 6, 7]
Check consecutive numbers in the said array!false

Flowchart:

Flowchart: Consecutive Numbers in an array.

For more Practice: Solve these Related Problems:

Write a Java program to check if an array can be rearranged into an arithmetic sequence.
Write a Java program to determine if an array contains all numbers in a given range.
Write a Java program to find the missing numbers in a sequence from a given array.
Write a Java program to check if an array can be rearranged to form a sequence with a constant difference.

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