I'm trying to search an item but the program gives incorrect result

Question

I wrote a program for linear search in python but it doesn's work correctly.

I tried double checking the program but I couldn't find the mistake.

def LinearSearch(arr, n):

    for i in arr:
        if i == n:
            return i
        else:
            return -1

def main():

    arr1 = [10, 20, 80, 30, 60, 50, 110, 100, 130, 170]
    n1 = 110

    arr2 = [10, 20, 80, 30, 60, 50, 110, 100, 130, 170]
    n2 = 175

    result1 = LinearSearch(arr1, n1)
    if result1 == n1:
        print('Item %d found at index %d' % (n1, result1))
    else:
        print('Item not found')

    result2 = LinearSearch(arr2, n2)
    if result2 == n2:
        print('Item %d found at index %d' % (n2, result2))
    else:
        print('Item not found')

main()

I expected output 'Element x is present at index 6' for the first search but it says 'Item not found'.

Answer 1

Since your LinearSearch function always met the return for any case and the function is just ended when it met return without looping. Thus, the function only gives -1 because the first element for each list is 10 which is not matching with 110 and 175.

Here is my modification.

def LinearSearch(arr, n):

    count = 0
    for i in arr:
        if i == n: return count
        else: count += 1
    return -1    

def main():

    arr1 = [10, 20, 80, 30, 60, 50, 110, 100, 130, 170]
    n1 = 110

    arr2 = [10, 20, 80, 30, 60, 50, 110, 100, 130, 170]
    n2 = 175

    result1 = LinearSearch(arr1, n1)
    if result1 != -1: print('Item %d found at index %d' % (n1, result1))
    else: print('Item not found')

    result2 = LinearSearch(arr2, n2)
    if result2 != -1: print('Item %d found at index %d' % (n2, result2))
    else: print('Item not found')

main()