Find Increasing Triplet Subsequence

gistfile1.txt

def find_triple(arr): #O(n)/O(1)
    mn = a = arr[0]
    b = None
    for v in arr[1:]:
        if mn >= v: # v is the new minimum
            mn = v
        elif b == None or b > v: # v > min but less than earlier 'b'
            a,b = mn,v
        else: # v > b > a  
            return a,b,v
    return None