过山车

#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

const int N = 510, M = 1010;

int h[N], e[M], ne[M], idx;
int n1, n2, m;
bool st[N];
int match[N];

void add(int a, int b) {
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}

bool find(int x) {
    for (int i = h[x]; i != -1; i = ne[i]) {

        int j = e[i];

        if (!st[j]) {
            st[j] = true;

            if (match[j] == 0 || find(match[j])) {
                match[j] = x;
                return true;
            }
        }
    }

    return false;
}

int main() {
    while (~scanf("%d", &m)) {
        if (m == 0)
            break;
        memset(h, -1, sizeof h);
        idx = 0;
        memset(match, 0, sizeof match);
        scanf("%d%d", &n1, &n2);

        while (m -- ) {
            int a, b;
            scanf("%d%d", &a, &b);
            add(a, b);
        }

        int res = 0;

        for (int i = 1; i <= n1; i ++ ) {

            memset(st, false, sizeof st);

            if (find(i))
                res ++ ;
        }

        printf("%d\n", res);
    }

    return 0;
}

Asteroids

#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

const int N = 510, M = 10010;

int h[N], e[M], ne[M], idx;
int n1, n2, m;
bool st[N];
int match[N];

void add(int a, int b) {
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}

bool find(int x) {
    for (int i = h[x]; i != -1; i = ne[i]) {

        int j = e[i];

        if (!st[j]) {
            st[j] = true;

            if (match[j] == 0 || find(match[j])) {
                match[j] = x;
                return true;
            }
        }
    }

    return false;
}

int main() {
    scanf("%d%d", &n1, &m);
    n2 = n1;
    memset(h, -1, sizeof h);

    while (m -- ) {
        int a, b;
        scanf("%d%d", &a, &b);
        add(a, b);
    }

    int res = 0;

    for (int i = 1; i <= n1; i ++ ) {

        memset(st, false, sizeof st);

        if (find(i))
            res ++ ;
    }

    printf("%d\n", res);


    return 0;
}

Antenna Placement

#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

const int N = 410;

int dx[] = {0, -1, 0, 1}, dy[] = {-1, 0, 1, 0};

int n, m;
bool st[N];
int match[N];
int mp[N][N];
bool g[N][N];
char op;
int id;
int n1, n2;

bool find(int x) {
    for (int i = 1; i <= n2; i ++ )

        if (g[x][i]) {
            if (!st[i]) {
                st[i] = true;

                if (match[i] == 0 || find(match[i])) {
                    match[i] = x;
                    return true;
                }
            }
        }

    return false;
}

int main() {
    int T;
    scanf("%d", &T);

    while (T -- ) {
        memset(match, 0, sizeof match);
        memset(g, false, sizeof g);
        memset(mp, 0, sizeof mp);
        id = 0;
        scanf("%d%d", &n, &m);

        for (int i = 0; i < n; i ++ )

            for (int j = 0; j < m; j ++ ) {

                cin >> op;

                if (op == '*')
                    mp[i][j] = ++ id;
                else
                    mp[i][j] = 0;
            }

        n1 = n2 = id;

        for (int i = 0; i < n; i ++ )

            for (int j = 0; j < m; j ++ )

                if (mp[i][j])
                    for (int k = 0; k < 4; k ++ ) {

                        int x = i + dx[k], y = j + dy[k];

                        if (mp[x][y])
                            g[mp[i][j]][mp[x][y]] = true;

                    }

        int res = 0;

        for (int i = 1; i <= n1; i ++ ) {

            memset(st, false, sizeof st);

            if (find(i))
                res ++ ;
        }

        printf("%d\n", id - res / 2);
    }

    return 0;
}