zoj2132-The Most Frequent Number

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=2132

The Most Frequent Number

Time Limit: 5 Seconds      Memory Limit: 1024 KB

Seven (actually six) problems may be somewhat few for a contest. But I am really unable to devise another problem related to Fantasy Game Series. So I make up an very easy problem as the closing problem for this contest.

Given a sequence of numbers A, for a number X if it has the most instances (elements of the same value as X) in A, then X is called one of the most frequent numbers of A. Now a sequence of numbers A of length L is given, and it is assumed that there is a number X which has more than L / 2 instances in A. Apparently X is the only one most frequent number of A. Could you find out X with a very limited memory?

Input

Input contains multiple test cases. Each test case there is one line, which starts with a number L (1 <= L <= 250000), followed by L numbers (-2^31 ~ 2^31-1). Adjacent numbers is separated by a blank space.

Output

There is one line for each test case, which is the only one most frequent number X.

Sample Input

5 2 1 2 3 2
8 3 3 4 4 4 4 3 4

Sample Output

2
4

思路:题意很简单,求一个数列里出现次数最多的那个数字,这个数字的个数是大于数列长度的1/2的。这里采用O(1)算法,利用大于1/2这个条件。

 1 #include <cstdio>
 2 
 3 int main()
 4 {
 5     int n,ans;
 6     while(~scanf("%d",&n))
 7     {
 8         int m,cnt=0;
 9         for(int i=0;i<n;i++)
10         {
11             scanf("%d",&m);
12             if(cnt==0)  ans=m,cnt++;
13             else if(ans==m) cnt++;
14             else    cnt--;
15         }
16         printf("%d\n",ans);
17     }
18     return 0;
19 }
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posted @ 2014-11-24 22:46  jiu~  阅读(253)  评论(0编辑  收藏  举报