[笔试] 在一个字符串中找到第一个只出现一次的字符

def find(str_):
    d = {}
    for s in str_:
        if s in d:
            d[s] += 1
        else:
            d[s] = 1
    for s in str_:
        if d[s] == 1:
            print(s)
            break

find("abaccdeff")