洛谷 偷天换日&&“访问”美术馆

典型的树形DP

按理说是先做“访问美术馆”再做偷天换日。

但是我先做了偷天换日然后再做的“访问”美术馆

DP方程好推，偷天换日在遇到有展品的时候做背包，因为是先做的偷天换日，所以把偷天换日的输入w,c直接将输入改为赋值就A了。

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#define MAXN 311
using namespace std;
struct node{
    int to, nxt, val;
}edge[MAXN << 1];
int flag, tot, n, head[MAXN], nxt[MAXN << 1], to[MAXN << 1], w[MAXN], val[MAXN << 1], dp[MAXN][MAXN << 1];
void add(int u, int v, int w) {
    edge[++tot].nxt = head[u], head[u] = tot, edge[tot].to = v, edge[tot].val = w;
    edge[++tot].nxt = head[v], head[v] = tot, edge[tot].to = u, edge[tot].val = w;
}
void dfs(int now) {
    int t, x, flag1;
    scanf("%d%d", &t, &x);
    add(now, ++flag, t << 1);
    if(!x) flag1 = flag, dfs(flag1), dfs(flag1);
    else for(int i = 1, c, w; i <= x; i++) {
        scanf("%d%d", &w, &c);
//        w = 1, c = 5;
        for(int j = n; j >= c; j--) dp[flag][j] = max(dp[flag][j], dp[flag][j - c] + w);
    }
}
void dfs1(int now, int fa) {
    for(int i = head[now]; i; i = edge[i].nxt)
        if(fa != edge[i].to) {
            dfs1(edge[i].to, now);
            for(int j = n; j >= 0; j--)
                for(int k = edge[i].val; k <= j; k++)
                    dp[now][j] = max(dp[now][j], dp[now][j - k] + dp[edge[i].to][k - edge[i].val]);
        }
}
int main() {
    scanf("%d", &n), n--;
    dfs(++flag);
    dfs1(1, 0);
    printf("%d", dp[1][n]);
    return 0;
}

 

 

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#define MAXN 311
using namespace std;
struct node{
    int to, nxt, val;
}edge[MAXN << 1];
int flag, tot, n, head[MAXN], nxt[MAXN << 1], to[MAXN << 1], w[MAXN], val[MAXN << 1], dp[MAXN][MAXN << 1];
void add(int u, int v, int w) {
    edge[++tot].nxt = head[u], head[u] = tot, edge[tot].to = v, edge[tot].val = w;
    edge[++tot].nxt = head[v], head[v] = tot, edge[tot].to = u, edge[tot].val = w;
}
void dfs(int now) {
    int t, x, flag1;
    scanf("%d%d", &t, &x);
    add(now, ++flag, t << 1);
    if(!x) flag1 = flag, dfs(flag1), dfs(flag1);
    else for(int i = 1, c, w; i <= x; i++) {
//        scanf("%d%d", &w, &c);
        w = 1, c = 5;
        for(int j = n; j >= c; j--) dp[flag][j] = max(dp[flag][j], dp[flag][j - c] + w);
    }
}
void dfs1(int now, int fa) {
    for(int i = head[now]; i; i = edge[i].nxt)
        if(fa != edge[i].to) {
            dfs1(edge[i].to, now);
            for(int j = n; j >= 0; j--)
                for(int k = edge[i].val; k <= j; k++)
                    dp[now][j] = max(dp[now][j], dp[now][j - k] + dp[edge[i].to][k - edge[i].val]);
        }
}
int main() {
    scanf("%d", &n), n--;
    dfs(++flag);
    dfs1(1, 0);
    printf("%d", dp[1][n]);
    return 0;
}

一世安宁