Algo: Linear Search

code:

/*
Count Frequency in an Array(Optimized Version)
Syed Ahmed Zaki -- 2017
*/
#include<stdio.h>
int linear_search(int A[],int n,int x)
{
    int i;
    for(i=0; i<n; i++)
        if(A[i]==x)
            return i;
    return -1;
}

int main()
{
    int x;
    int A[]= {5,6,7,8,9};
    printf("Put value to search from an array:\n");
    scanf("%d",&x);
    int out=linear_search(A,5,x);
    if(out==-1)
    {
        printf("%d is not found\n",x);
    }
    else
    {
        printf("%d is in index %d\n",x,out);
    }
    return 0;

}

Another Code By Me:

/*
Count Frequency in an Array(Optimized Version)
Syed Ahmed Zaki -- 2017
*/
#include<stdio.h>
int linear_search(int *A,int n,int x) //*A is passing the value of the array address index
{
    int i;
    for(i=0; i<n; i++)
        if(A[i]==x)
            return i;
    return -1;
}

int main()
{
    int x,i,n;
    printf("Array Size:");
    scanf("%d",&n);
    int A[10005];
    printf("Please enter an array elements:");
    for(i=0;i<n;i++)
    {
        scanf("%d",&A[i]);
    }
    printf("Put value to search from an array:\n");
    scanf("%d",&x);
    int out=linear_search(A,5,x);
    if(out==-1)
    {
        printf("%d is not found\n",x);
    }
    else
    {
        printf("%d is in index %d\n",x,out);
    }
    return 0;

}

Complexity:
Best Case: O(1)
Worst Case: O(n)
Average Case: O(n/2)=O(n)
Source: http://quiz.geeksforgeeks.org/linear-search/

Pseudocode Looks Like this:

SEARCH(A, v):
  for i = 1 to A.length
      if A[i] == v
          return i
  return NIL

source: http://clrs.skanev.com/02/01/03.html

Another Good Pseudocode:

LinearSearch(A,n,item)
Begin
 for i=0 to n-1 by 1 do
    if A[i]==item then
      return i;
    end if
 end for
 return -1
End

Source: