matching

bool dfs(int x) {
    visited[x] = 1;
    for (int i: adj[x]) {
        if (match[i]==-1 || (!visited[match[i]] && dfs(match[i]))) {
            match[i] = x;
            return 1;
        }
    }
    return 0;
}

int matching() {
    int ans = 0;
    for (int i=0;i<M;i++) match[i] = -1;
    for (int i=0;i<N;i++) {
        for (int j=0;j<N;j++) visited[j] = 0;
        ans+=dfs(i);
    }
    return ans;
}