[luoguP1272] 重建道路

传送门

奇奇怪怪的分组背包。

#include <cstdio>
#include <cstring>
#include <iostream>
#define N 151
#define min(x, y) ((x) < (y) ? (x) : (y))

int n, p, cnt, ans = ~(1 << 31);
int head
, to
, next
, f

;

inline int read()
{
int x = 0, f = 1;
char ch = getchar();
for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1;
for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0';
return x * f;
}

inline void dfs(int u)
{
int i, j, k, v;
for(i = head[u]; i ^ -1; i = next[i])
{
v = to[i];
dfs(v);
for(j = p; j >= 1; j--)
for(k = 1; k < j; k++)
f[u][j] = min(f[u][j], f[u][j - k] + f[v][k] - 2);
}
}

inline void add(int x, int y)
{
to[cnt] = y;
next[cnt] = head[x];
head[x] = cnt++;
}

int main()
{
int i, x, y;
n = read();
p = read();
memset(f, 127 / 3, sizeof(f));
memset(head, -1, sizeof(head));
for(i = 1; i <= n; i++) f[i][0] = f[i][1] = 0;
for(i = 1; i < n; i++)
{
x = read();
y = read();
add(x, y);
f[x][1]++;
f[y][1]++;
}
dfs(1);
for(i = 1; i <= n; i++) ans = min(ans, f[i]
);
printf("%d\n", ans);
return 0;
}