hdu_1054_Strategic Game

树形dp，状态：dp[u][1], dp[u][0]分别表示第u个节点放与不放兵状态转移方程表示为:dp[u][0] = sum{dp[v[1]};dp[u][1] = sum{dp[v][0], dp[v][1]}ans = min(dp[root][0], dp[root][1]);#include <cstdio>#include <cstring>#include <algorithm>using namespace std;#define SELECT          1#define UNSELECT        0#define MAXN            1510#define MAXM            10000struct EDGE {        int v, next;}edge[MAXM];int head[MAXN], dp[MAXN][2], is_root[MAXN], e_cnt;void insert_arc(const int &u, const int &v){        edge[e_cnt].v = v; edge[e_cnt].next = head[u]; head[u] = e_cnt ++;}int build_tree(const int &node_cnt){        char tmp[MAXN/100];        int src, des, child_cnt;        memset(is_root, -1, sizeof(is_root));        e_cnt = 0; memset(head, -1, sizeof(head));        for(int i = 0; i < node_cnt; i ++) {                scanf("%s", tmp); sscanf(tmp, "%d:(%d)", &src, &child_cnt);                for(int j = 0; j < child_cnt; j ++) {                        scanf("%d", &des);                        is_root[des] = 0; insert_arc(src, des);                }        }        for(int i = 0; i < node_cnt; i ++) {                if( is_root[i] ) {                        return i;                }        }}int dfs(const int &u, const int &mark){        if( -1 != dp[u][mark] ) {                return dp[u][mark];        }        if( -1 == head[u] ) {                return mark;        }        dp[u][mark] = mark;        for(int i = head[u]; -1 != i; i = edge[i].next) {                dp[edge[i].v][mark] = (-1 == dp[edge[i].v][mark])? dfs(edge[i].v, mark) : dp[edge[i].v][mark];                dp[edge[i].v][!mark] = (-1 == dp[edge[i].v][!mark])? dfs(edge[i].v, !mark) : dp[edge[i].v][!mark];                dp[u][mark] += (mark)?min(dp[edge[i].v][!mark], dp[edge[i].v][mark]) : dp[edge[i].v][!mark];        }        return dp[u][mark];}int main(int argc, char const *argv[]){#ifndef ONLINE_JUDGE        freopen("test.in", "r", stdin);#endif                int node_cnt, root;        while( ~scanf("%d", &node_cnt) ) {                root = build_tree(node_cnt);                memset(dp, -1, sizeof(dp));                printf("%d\n", min(dfs(root, SELECT), dfs(root, UNSELECT)));        }        return 0;}