hdu 5210 hash统计或stl

方法1：

#include <iostream>
#include <cstring>
using namespace std;

const int N = 101;
int cnt[N];

int main()
{
    int n, k;
    while ( cin >> n )
    {
        memset( cnt, 0, sizeof(cnt) );
        for ( int i = 1; i <= n; i++ )
        {
            int tmp;
            cin >> tmp;
            cnt[tmp]++;
        }
        cin >> k;        
        int kinds = 0;
        for ( int i = 1; i <= n; i++ )
        {
            if ( cnt[i] ) kinds++;
        }
        int sum = n - kinds;
        if ( sum < k )
        {
            k -= sum;
            kinds -= k;
        }
        cout << kinds << endl;
    }
    return 0;
}

方法2：

引入set判断重复，代码只有些许改变。

#include <iostream>
#include <set>
using namespace std;

int main()
{
    int n, k;
    while ( cin >> n )
    {
        set<int> s;
        for ( int i = 1; i <= n; i++ )
        {
            int tmp;
            cin >> tmp;
            s.insert(tmp);
        }
        cin >> k;        
        int kinds = s.size(), sum = n - kinds;
        if ( sum < k )
        {
            k -= sum;
            kinds -= k;
        }
        cout << kinds << endl;
    }
    return 0;
}