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)