素数伴侣，匈牙利算法

# include <iostream>
# include <math.h>
# include <vector>
using namespace std;

bool is_prime(int num)
{
    if(num == 1)
        return false;
    for(int i = 2; i * i <= num; i++)
        if (num % i == 0)
            return false;
    return true;
}
bool find(int odd, vector<int>& evens, vector<bool>& used, vector<int>& match)
{
    for(int i = 0; i < evens.size(); i++)
    {
        if(is_prime(odd + evens[i]) && !used[i])
        {
            used[i] = true;
            if(match[i] == 0 || find(match[i], evens, used, match)) //先到先得，能让则让
            {
                match[i] = odd;
                return true;
            }
        }
    }
    return false;
}
int main()
{
    int n, temp;
    while(cin >> n)
    {
        vector<int> odds, evens;
        for(int i = 0; i < n; i++)
        {
            cin >> temp;
            if(temp % 2)
                odds.push_back(temp);
            else
                evens.push_back(temp);
        }
        if(!odds.size() || !evens.size())
        {
            cout << 0 << endl;
            continue;
        }
        // 暴力匈牙利算法进行匹配
        vector<int> match(evens.size(), 0);
        int count = 0;
        for(int odd:odds)
        {
            vector<bool> used(evens.size(), false); //每一轮偶数都没用过（能让则让）
            if(find(odd, evens, used, match))
                count++;
        }
        cout << count << endl;
    }
    return 0;
}

# include <iostream>
# include <math.h>
# include <vector>
using namespace std;

bool is_prime(int num)
{
    if(num == 1)
        return false;
    for(int i = 2; i * i <= num; i++)
        if (num % i == 0)
            return false;
    return true;
}
bool find(int index, vector<int>& evens, vector<bool>& used, vector<int>& match, vector<vector<bool>>& map)
{
    for(int i = 0; i < evens.size(); i++)
    {
        if(map[i][index] && !used[i])
        {
            used[i] = true;
            if(match[i] == -1 || find(match[i], evens, used, match, map)) //先到先得，能让则让
            {
                match[i] = index;
                return true;
            }
        }
    }
    return false;
}

void map_h(vector<int> odds, vector<int> evens, vector<vector<bool>>& map)
{
    for(int i = 0; i < evens.size(); i++)
        for(int j = 0; j < odds.size(); j++)
            if(is_prime(odds[j] + evens[i]))
                map[i][j] = true;
}

int main()
{
    int n, temp;
    while(cin >> n)
    {
        vector<int> odds, evens;
        for(int i = 0; i < n; i++)
        {
            cin >> temp;
            if(temp % 2)
                odds.push_back(temp);
            else
                evens.push_back(temp);
        }
        if(!odds.size() || !evens.size())
        {
            cout << 0 << endl;
            continue;
        }
        vector<vector<bool>> map(evens.size(), vector<bool>(odds.size(), false));
        map_h(odds, evens, map);
        // 哈希表优化的匈牙利算法进行匹配
        vector<int> match(evens.size(), -1);
        int count = 0;
        for(int i = 0; i < odds.size(); i++)
        {
            vector<bool> used(evens.size(), false); //每一轮偶数都没用过（能让则让）
            if(find(i, evens, used, match, map))
                count++;
        }
        cout << count << endl;
    }
    return 0;
}