Python

arr1, arr2 = [1, 3, 2, 7, 4], [12, 1, 3, 6, 8, 7, 4]

Solution 1 (O(n*m)):

inxsn = []
for i in arr1:
    for j in arr2:
        if i == j:
            inxsn.append(i)
            break

print(inxsn)
#→ [1, 3, 7, 4]

Solution 2 (O(n)):

inxsn = []
for i in arr1:
    if i in arr2:
        inxsn.append(i)

print(inxsn)
#→ [1, 3, 7, 4]

Solution 3: List comprehension

print(
	[i for i in arr1 if i in arr2]
)
#→ [1, 3, 7, 4]