Description

This program is for finding missing odd number in first n odd number. 

The (n-1) odd number will be any random odd number in the range of first n odd number.

The difference between summation of first n odd number and summation of given (n-1)
odd number will give the missing odd number.

C/C++

/* C program to Find missing odd number in first n odd number */
//Save it as FindMissingOddNumber.c

#include<stdio.h>
int main(){

    int n;

    printf("Enter the size of array : ");
    scanf("%d",&n);

    //Declaring array for first n odd number
    int arrOdd[n];
    //Declaring array for n-1 odd number out of n odd number to be entered by user
    int arrGiven[n-1];

    int i;

    //Variable to find sum of entered odd number
    int sumGiven=0;
    //Variable to find sum of first n odd number
    int sumOdd=0;

    int count=0;

    printf("Enter %d odd numbers in first %d odd number : ",n-1,n);
    for(i=0;i<n-1;i++) {
        scanf("%d",&arrGiven[i]);
        //Finding sum of entered elements
        sumGiven += arrGiven[i];
    }

    printf("Entered elements are : ");
    for(i=0;i<n-1;i++) {
        printf("%d ",arrGiven[i]);
    }

    //Finding first n odd number
    for(i=0;i<=(n*2);i++) {
        if(i%2 != 0) {
            arrOdd[count++] = i;
            //Finding sum of first n odd numbers
            sumOdd += i;
        }
    }

    printf("\nThe first %d odd numbers of array are : ",count);
    for(i=0;i<count;i++) {
        printf("%d ",arrOdd[i]);
    }

    //Printing the missing odd number in first n odd number
    printf("\nMissing odd number is : %d",(sumOdd-sumGiven));

    return 0;
}

Input:
Enter the size of array : 
7
Enter 6 odd numbers in first 7 odd number : 
3
9
1
5
13
7

Output:
Entered elements are : 
3 9 1 5 13 7 
The first 7 odd numbers of array are : 
1 3 5 7 9 11 13 
Missing odd number is : 11

Java

/* Java program to Find missing odd number in first n odd number */
//Save it as FindMissingOddNumber.java

import java.io.*;
import java.util.Scanner;

public class FindMissingOddNumber {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        
        System.out.println("Enter the size of array : ");
        int n = scanner.nextInt();
        
                //Declaring array for first n odd number
        int arrOdd[] = new int[n];
                //Declaring array for n-1 odd number out of n odd number to be entered by user
        int arrGiven[] = new int[n-1];
        
        int i;
        
                //Variable to find sum of entered odd number
        int sumGiven=0;
                //Variable to find sum of first n odd number
        int sumOdd=0;

        int count=0;
        
        System.out.println("Enter "+(n-1)+" odd numbers in first "+n+" odd number : ");
        for(i=0;i<n-1;i++) {
            arrGiven[i] = scanner.nextInt();
                        //Finding sum of entered elements
            sumGiven += arrGiven[i];
        }
        
        System.out.println("Entered elements are : ");
        for(i=0;i<n-1;i++) {
            System.out.print(arrGiven[i]+" ");
        }
        
                //Finding first n odd number
        for(i=0;i<=(n*2);i++) {
            if(i%2 != 0) {
                arrOdd[count++] = i;
                            //Finding sum of first n odd numbers
                sumOdd += i;
            }
        }	
        
        System.out.println("\nThe first "+count+" odd numbers of array are : ");
        for(i=0;i<count;i++) {
            System.out.print(arrOdd[i]+" ");
        }
        
                //Printing the missing odd number in first n odd number
        System.out.println("\nMissing odd number is : "+(sumOdd-sumGiven));
    }
}

Input:
Enter the size of array : 
7
Enter 6 odd numbers in first 7 odd number : 
3
9
1
5
13
7

Output:
Entered elements are : 
3 9 1 5 13 7 
The first 7 odd numbers of array are : 
1 3 5 7 9 11 13 
Missing odd number is : 11

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