Question

A list contains a set of numbers, one number presents once and other numbers present even no. of times. Find out the number that occurs once in the list.

Answer 1

Following C program gives the expected.

 #include<stdio.h>
    int main()
    {
       int numList[] = { 12, 12, 14, 14, 15, 15, 16 };
       int diffNum = 0;
       int i;
       int totalNum  = sizeof(numList)/sizeof(numList[0]);

       for (i=0; i < totalNum; i++)
       {
          diffNum ^= numList[i];
       }

       printf("Different Number = [%d]", diffNum);

       return 0;
    }

Comments

This is the best answer.

Answer 2

Just wanted to add little bit complexity in what Harshita had mentioned. This might help you.

include <stdio.h>

int main()
{
int a[] = {1,3,3,1,3,4,4,6,1,6,1};
int n = sizeof(a)/sizeof(a[0]);
int i = 0, j = 0;

for(i = 0; i < n; i++){
    for(j = i+1; j < n; j++){
        if(a[i] == a[j]){
            a[j] = -a[j];
            break;
        }
    }
    if(i != n-1){
        printf("i %d\n",i);
        if(a[i] != a[j]){
            if(a[i] == -(a[j])){
                continue;
            }else if(a[i] < 0){
                continue;
            }else{
                printf("Unique Number [%d]\n",a[i]);
                break;
            }
        }
    }else{
        printf("Unique Number [%d]\n",a[i]);
        break;
    }
}
return 0;

}