Find the second largest element in an integer array,without using sorting techniques and complexity must not exceed O(n)

Question

Given an unordered array A of size n and integer x. What is the best complexity to find two elements in A whose sum is x?
Share the algo, its complexity and if possible C code.

Answer 1

Please find my answer as following:

Input - 13, 2, 41, 5 , 46, 7
first_big = 12 // first big
second_big = 2 // second big

for (i = 2; i < size - 1; i++)
{
if (arr[i] > first_big)
{
second_big = first_big;
first_big = arr[i];
}
}

First iteration:

second_big = 12
first_big = 41

Second iteration:

No change

Third iteration:

second_big = 41
first_big = 46

This is final result.
If someone has better logic to solve this problem then please share.

Comments

your logic can't be applied on any input i guess. output in:41 46 12 3 17 1 is first_big=41 and second_big=46  and output in 41 46 12 3 98 1 is first big=98,second big=41.in both cases output is wrong.please let me know if i understood your logic wrong, i guess u have taken the first and second integer of the array as first_big and second_big.
however slightly modified version works fine.
int main()
 {
     int arr[]={41,12,18,46,1};
     int second_big;
     int first_big=arr[0]>arr[1]?arr[0]:arr[1];
     if(first_big==arr[0])
        second_big=arr[1];
    else
        second_big=arr[0];
  for (i = 2; i < size ; i++)
    {
         if (arr[i] > first_big)
           {
             second_big = first_big;
             first_big = arr[i];
          }
  printf("%d",second_big);
}
  return 0;
 }

Answer 2

Find the 2nd highest element:

int findSecondHighest(int *arr,int len){

     int max=0,second_highest,i;
     for(i=0;i<len;i++){
         if(max<arr[i]){
                    max=arr[i];
                    second_highest=max;
                 }
           }
      return second_highest;
}

Time Complexity=O(n)