P2014 [CTSC1997]选课

P2014 [CTSC1997]选课

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>
#include <queue>
#include <map>
#include <sstream>
#include <cstdio>
#include <cstring>
#include <numeric>
#include <cmath>
#include <iomanip>
#include <deque>
#include <bitset>
#include <cassert>
//#include <unordered_set>
//#include <unordered_map>
#define ll              long long
#define pll             pair<ll, ll>
#define pii             pair<int, int>
#define rep(i,a,b)      for(int  i=a;i<=b;i++)
#define dec(i,a,b)      for(int  i=a;i>=b;i--)
#define forn(i, n)      for(int i = 0; i < int(n); i++)
using namespace std;
int dir[4][2] = { { 1,0 },{ 0,1 } ,{ 0,-1 },{ -1,0 } };
const long long INF = 0x7f7f7f7f7f7f7f7f;
const int inf = 0x3f3f3f3f;
const double pi = acos(-1.0);
const double eps = 1e-6;
const ll mod = 1e9 + 7;

template<typename T>void read(T & x) {
    T f = 1; x = 0; char s = getchar();
    while (s < '0' || s > '9') { if (s == '-')f = -1; s = getchar(); }
    while (s >= '0' && s <= '9') { x = x * 10 + s - '0'; s = getchar(); }
    x *= f;
}

template<typename T>void print(T x) {
    if (x < 0) putchar('-'), x = -x;
    if (x > 9) print(x / 10);
    putchar(x % 10 + '0');
}

/**********************************************************/
const int N = 300 + 5;

int n, m;
int dp[N][N];
vector<int> g[N];

int dfs(int x)
{
    int sz = 1;
    for (auto to : g[x])
    {
        int p = dfs(to);
        dec(i, min(m + 1, sz), 1)
        {
            for (int j = 1; j <= p && j + i <= m + 1; j++)
            {
                dp[x][i + j] = max(dp[x][i + j], dp[x][i] + dp[to][j]);
            }
        }
        sz += p;
    }
    return sz;
}

int main()
{
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    cin >> n >> m;
    rep(i, 1, n)
    {
        int u;
        cin >> u >> dp[i][1];
        g[u].push_back(i);
    }
    dfs(0);
    cout << dp[0][m + 1] << endl;
    return 0;
}