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| #include <iostream>
#include <cstdio>
#include <cstring>
#include <cctype>
#define maxn 10010
#define maxm 11
#define INF 1000000000
#define gc getchar
using namespace std;
int read() {
int x = 0; char c = gc();
while (!isdigit(c)) c = gc();
while (isdigit(c)) x = x * 10 + c - '0', c = gc();
return x;
}
int n, s, m;
struct Edge {
int to, next, w;
} e[maxn * 2]; int c1, head[maxn];
inline void add_edge(int u, int v, int w) {
e[c1].to = v; e[c1].w = w;
e[c1].next = head[u]; head[u] = c1++;
}
int f[maxn][maxm];
void dfs(int u, int fa) {
for (int i = head[u]; ~i; i = e[i].next) {
int v = e[i].to, w = e[i].w; if (v == fa) continue; dfs(v, u);
for (int j = m; j >= 0; --j) {
f[u][j] += f[v][0] + 2 * w;
for (int k = 1; k <= j; ++k)
f[u][j] = min(f[u][j], f[u][j - k] + f[v][k] + k * w);
}
}
}
void init() {
memset(head, -1, sizeof head); c1 = 0;
memset(f, 0, sizeof f);
}
void work() { init();
for (int i = 1; i < n; ++i) {
int x = read(), y = read(), z = read();
add_edge(x, y, z); add_edge(y, x, z);
} dfs(s, 0);
cout << f[s][m] << endl;
}
int main() {
while (cin >> n >> s >> m) work();
return 0;
}
|