(Arrays.sort() 或 map) Ignatius and the Princess IV hdu1029

Posted 2021-01-06 weixu-liu

Ignatius and the Princess IV

链接：http://acm.hdu.edu.cn/showproblem.php?pid=1029

借鉴链接：https://blog.csdn.net/tigerisland45/article/details/52146154

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32767 K (Java/Others)
Total Submission(s): 43810    Accepted Submission(s): 19319

Problem Description

"OK, you are not too bad, em... But you can never pass the next test." feng5166 says.

"I will tell you an odd number N, and then N integers. There will be a special integer among them, you have to tell me which integer is the special one after I tell you all the integers." feng5166 says.

"But what is the characteristic of the special integer?" Ignatius asks.

"The integer will appear at least (N+1)/2 times. If you can‘t find the right integer, I will kill the Princess, and you will be my dinner, too. Hahahaha....." feng5166 says.

Can you find the special integer for Ignatius?

 

 

Input

The input contains several test cases. Each test case contains two lines. The first line consists of an odd integer N(1<=N<=999999) which indicate the number of the integers feng5166 will tell our hero. The second line contains the N integers. The input is terminated by the end of file.

 

 

Output

For each test case, you have to output only one line which contains the special number you have found.

 

 

Sample Input

5

1 3 2 3 3

11

1 1 1 1 1 5 5 5 5 5 5

7 1 1 1 1 1 1 1

 

 

Sample Output

3

5

1

 

 

Author

Ignatius.L

 

这个题的题意就是：

输入n（n是奇数），然后输入n个整数，求其中至少出现(n+1)/2次的整数（至少有(n+1)/2个整数）。

思路：

n是奇数，(n+1)/2是n的一半以上，只要将n个数据排序，出现(n+1)/2次的整数必然会出现在中间位置。

 

JAVA代码：

import java.util.Arrays;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner inScanner = new Scanner(System.in);
        while(inScanner.hasNext()) {
            int n = inScanner.nextInt();
            int[] x = new int[n];  //要掌握java的数组初始化的用法。
            for(int i = 0;i<n;i++) {
                x[i] = inScanner.nextInt();
            }
            Arrays.sort(x); //注意sort的用法，记住。
            System.out.println(x[(n+1)/2]);
        }
    }

}

 

C++代码：（用了map（），思路有点复杂）

#include <iostream>
#include <map>
using namespace std;
int main()
{
    int n;
    map<int,int> a;
    while(cin>>n)
    {
        a.clear();
        int m;
        int b=n;
        while(b--)
        {
            cin>>m;
            a[m]++;
        }
        for(map<int,int>::iterator it=a.begin();it!=a.end();it++)
        {
            if(it->second>=(n+1)/2)
            {
                cout<<it->first<<endl;
                break;
            }
        }
    }
    return 0;
}