UVa 1292 Strategic game

有两种做法：一种是经典二分图最小顶点覆盖，一种是树形DP，我用的后者。

第一次学习树形DP……

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <vector>
#include <algorithm>

using namespace std;

const int MAXN = 1600;

int N, root;
int dp[MAXN][2];
vector<int> tree[MAXN];

void init()
{
    root = -1;

    for ( int i = 0; i < N; ++i )
    {
        int u, cnt;
        tree[i].clear();
        scanf("%d:(%d)", &u, &cnt );
        if ( root == -1 ) root = u;
        for ( int j = 0; j < cnt; ++j )
        {
            int v;
            scanf( "%d", &v );
            tree[u].push_back(v);
        }
    }
    return;
}

int DFS( int fa )
{
    dp[fa][0] = 0;
    dp[fa][1] = 1;
    int len = tree[fa].size();
    for ( int i = 0; i < len; ++i )
    {
        int v = tree[fa][i];
        DFS( v );
        dp[fa][0] += dp[v][1];
        dp[fa][1] += min( dp[v][0], dp[v][1] );
    }
    return min( dp[fa][0], dp[fa][1] );
}

int main()
{
    while ( scanf( "%d", &N ) == 1 )
    {
        init();
        printf( "%d\n", DFS(root) );
    }
    return 0;
}