洛谷 P1364 医院设置

Posted on Edited on In 
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#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 101, M = 2 * N;
int n, u, v, h[N], w[M], e[M], ne[M], idx;
int ans = 1e9;
bool visited[N];
struct node {
    int u, s;
    node() {}
    node(int idx, int step) : u(idx), s(step) {}
};
node q[N];
void add(int u, int v) {
    e[idx] = v, ne[idx] = h[u], h[u] = idx++;
}
int bfs(int x) {
    int sum = 0;
    memset(visited, false, n + 1);
    visited[x] = true;
    int hh = 0, tt = -1;
    q[++tt] = node(x, 1);
    while (hh <= tt) {
        auto[u, s] = q[hh++];
        for (int i = h[u]; ~i; i = ne[i]) {
            int v = e[i];
            if (visited[v]) continue;
            q[++tt] = node(v, s + 1);
            visited[v] = true;
            sum += w[v] * s;
        }
    }
    return sum;
}
int main() {
    scanf("%d", &n);
    memset(h, -1, (n + 1) * 4);
    for (int i = 1; i <= n; ++i) {
        scanf("%d%d%d", &w[i], &u, &v);
        if (u) add(i, u), add(u, i);
        if (v) add(i, v), add(v, i);
    }
    for (int i = 1; i <= n; ++i) ans = min(ans, bfs(i));
    printf("%d\n", ans);
    return 0;
}
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#include <bits/stdc++.h>
using namespace std;
const int N = 101, INF = INT_MAX;
int ans = INF;
int d[N][N];
int n, u, v, w[N];
int main() {
    scanf("%d", &n);
    fill(d[0], d[0] + N * N, INF);
    for (int i = 1; i <= n; ++i) {
        scanf("%d%d%d", &w[i], &u, &v);
        if (u) d[i][u] = d[u][i] = 1;
        if (v) d[i][v] = d[v][i] = 1;
    }
    for (int k = 1; k <= n; ++k)
        for (int i = 1; i <= n; ++i)
            for (int j = 1; j <= n; ++j)
                if (d[i][k] < INF && d[k][j] < INF)
                    d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
    for (int i = 1; i <= n; ++i) {
        int sum = 0;
        for (int j = 1; j <= n; ++j)
            if (i != j)
                sum += w[j] * d[i][j];
        ans = min(ans, sum);
    }
    printf("%d", ans);
    return 0;
}
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#include <bits/stdc++.h>
using namespace std;
const int N = 101, M = 2 * N;
int n, u, v, h[N], w[M], e[M], ne[M], idx;
int ans = 1e9;
bool visited[N];
void add(int u, int v) {
    e[idx] = v, ne[idx] = h[u], h[u] = idx++;
}
int dfs(int u, int s) {
    int sum = s * w[u];
    for (int i = h[u]; ~i; i = ne[i]) {
        int v = e[i];
        if (visited[v]) continue;
        visited[v] = true;
        sum += dfs(v, s + 1);
    }
    return sum;
}
int main() {
    scanf("%d", &n);
    memset(h, -1, (n + 1) * 4);
    for (int i = 1; i <= n; ++i) {
        scanf("%d%d%d", &w[i], &u, &v);
        if (u) add(i, u), add(u, i);
        if (v) add(i, v), add(v, i);
    }
    for (int i = 1; i <= n; ++i) {
        memset(visited, false, n + 1);
        visited[i] = true;
        ans = min(ans, dfs(i, 0));
    }
    printf("%d\n", ans);
    return 0;
}
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#include <bits/stdc++.h>
using namespace std;
const int N = 101, M = 2 * N;
int n, u, v, h[N], w[M], e[M], ne[M], idx;
int deep[N], dist[N], sum[N];
int ans;
void add(int u, int v) {
    e[++idx] = v, ne[idx] = h[u], h[u] = idx;
}
void dfs(int u, int f) {
    deep[u] = deep[f] + 1;
    for (int i = h[u]; i; i = ne[i]) {
        int v = e[i];
        if (v == f) continue;
        dfs(v, u);
        sum[u] += sum[v];
    }
}
int dp(int u, int f) {
    for (int i = h[u]; i; i = ne[i]) {
        int v = e[i];
        if (v == f) continue;
        dist[v] = dist[u] + sum[1] - sum[v] - sum[v];
        ans = min(ans, dist[v]);
        dp(v, u);
    }
}
int main() {
    scanf("%d", &n);
    for (register int i = 1; i <= n; ++i) {
        scanf("%d%d%d", &w[i], &u, &v);
        sum[i] = w[i];
        if (u) add(i, u), add(u, i);
        if (v) add(i, v), add(v, i);
    }
    deep[0] = 0;
    dfs(1, 0);
    for (register int i = 1; i <= n; ++i)
        dist[1] += (deep[i] - 1) * w[i];
    ans = dist[1];
    dp(1, 0);
    printf("%d\n", ans);
    return 0;
}