PYTHON

How to find the three largest values of an array efficiently, in Python?

"""
This implementation finds the three largest
numbers in an array in an efficient manner.

The idea is to maintain a subarray holding
the three largest values encountered so 
far. When the algorithm concludes that 
subarray would end up holding the desired
output value (i.e., 3 largest values of 
main array).

Let n be the size of the array
Time complexity: O(n)
Space complexity: O(1)
"""
def find_three_largest_values(arr):
    # Container for 3 largest values
    result = [None]*3
    # Make sure result holds always
    # 3 largest values encountered so far
    for val in arr:
        update_result(result, val)
    return result

def update_result(result, val):
    # Insert val into appropriate position
    # Only vals of interest are those bigger
    # than values already in result array.
    if result[2] is None or val > result[2]:
        update_and_shift(result, val, 2)
    elif result[1] is None or val > result[1]:
        update_and_shift(result, val, 1)
    elif result[0] is None or val > result[0]:
        update_and_shift(result, val, 0)

def update_and_shift(result, val, idx):
    for i in range(idx+1):
        if i == idx:
            result[i] = val
        else:
            result[i] = result[i+1]

arr = [1, 2, 3, 7, 8, 9]
print(find_three_largest_values(arr))  # [7, 8, 9]

python find in largest 3 numbers in an array

array = [1, 2, 3, 4, 5, 6, 7, 8, 9, ]
result = []
num = int(input('Enter N: '))

for x in range(0, num):
    largeNum = 0
    for y in range(len(array)):
        if array[y] > largeNum:
            largeNum = array[y]
    array.remove(largeNum)
    result.append(largeNum)

print(result)