Write a Program to find the deleted number from an array

Program to find the deleted number from an array

Suppose you have an array of number 1-50 in random order. The number in an array is not repeated. One number is deleted from an array find the deleted number.


Logic of a Program


1. The number is not repeated so we can calculate the sum of first 50 number. The sum of number  is n(n+1)/2 = 50*(50+1)/2


2. Now one number is deleted from an array, calculate the sum of remaining number using single pass

int sum =0;

for(int i=0;i<49;i++){

      sum = sum + arr[i];

}

Now subtract this sum to the original sum. You will find the missing number.


Hope this is useful. If you know any other solution please comment below.