PYTHON

first duplicate

def solution(a):
    
    arr = []
    
    for i in range(len(a)):
        for j in range(i+1,len(a)):
            if a[i]==a[j]:
                hash.append(j)
    if len(hash) == 0:
        return -1
    else:
        idx = min(hash)
        return a[idx]

a = [2, 3, 4, 6, 5, 3]
Solution(a)

first duplicate

def Solution(a):
  arr = []
  value=[]
  for i in range(len(a)):
    if a[i] not in hash:
      hash.append(a[i])
    else:
      value.append(i)
  if len(value) ==0:
    return -1
  else:
    idx = min(value)
    return a[idx]

# a = [1,2,3,4,4,2]
a=[1,2,3,4]
Solution(a)