Python实现Pat 1041. Be Unique (20)

题目

Being unique is so important to people on Mars that even their lottery is designed in a unique way. The rule of winning is simple: one bets on a number chosen from [1, 104]. The first one who bets on a unique number wins. For example, if there are 7 people betting on 5 31 5 88 67 88 17, then the second one who bets on 31 wins.

Input Specification:

Each input file contains one test case. Each case contains a line which begins with a positive integer N (<=105) and then followed by N bets. The numbers are separated by a space.

Output Specification:

For each test case, print the winning number in a line. If there is no winner, print “None” instead.

Sample Input 1:

7 5 31 5 88 67 88 17

Sample Output 1:

31

Sample Input 2:

5 888 666 666 888 888

Sample Output 2:

None

解答1，会超时

#直接检查每一个数值点是否唯一
line=[int(x) for x in input().split(' ')]
N=line[0]
seq=line[1:]
for i in range(N):
tmp=seq[:]
tmp.pop(i)
if seq[i] not in tmp:
print (seq[i])
break
else:
print(None)

解答2

#利用哈希映射，统计各数值点出现的次数，再检查次数是否为1
line=[int(x) for x in input().split(' ')]
N=line[0]
seq=line[1:]
tag=[0]*100000#一个恰当大的数值，过小返回非零，过大内存超限
for c in seq:
tag[c]+=1
for i in range(N):
if tag[seq[i]]==1:
print(seq[i])
break
else:
print(None)