反思ing

写了一道许久之前写过的题，发现好久没写线段树了和图之类的东西，现在都很生疏了，一定要加强锻炼，增强代码能力，加油。

HDU5195

#include <cstdio>
#include <vector>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;
#define N 100000 + 10
#define INF 0x3f3f3f3f
#define lson L, mid, rt << 1
#define rson mid + 1, R, rt << 1 | 1

int n, m, k, tot, head[N], deg[N], Min[N << 2];
vector<int> ans;
struct Edge
{
    int v, next;
}e[N];

void init()
{
    tot = 0;
    memset(deg, 0, sizeof deg);
    memset(head, -1, sizeof head);
}

void adde(int u, int v)
{
    deg[v]++;
    e[tot].v = v;
    e[tot].next = head[u];
    head[u] = tot++;
}

void pushup(int rt)
{
    Min[rt] = min(Min[rt << 1], Min[rt << 1 | 1]);
}

void build(int L, int R, int rt)
{
    if(L == R)
    {
        Min[rt] = deg[L];
        return ;
    }
    int mid = (L + R) >> 1;
    build(lson); build(rson);
    pushup(rt);
}

void update(int q, int v, int L, int R, int rt)
{
    if(L == R)
    {
        Min[rt] = v;
        return ;
    }
    int mid = (L + R) >> 1;
    if(q <= mid) update(q, v, lson);
    else update(q, v, rson);
    pushup(rt);
}

int query(int k, int L, int R, int rt)
{
    if(L == R)
    {
        return L;
    }
    int mid = (L + R) >> 1;
    if(Min[rt << 1 | 1] <= k) return query(k, rson);
    else return query(k, lson);
}

int main()
{
    while(~scanf("%d%d%d", &n, &m, &k))
    {
        init();
        int u, v;
        ans.clear();
        for(int i = 0; i < m; i++)
        {
            scanf("%d%d", &u, &v);
            adde(u, v);
        }

        build(1, n, 1);

        for(int i = 1; i <= n; i++)
        {
            int id = query(k, 1, n, 1);
            k -= deg[id];
            ans.push_back(id);
            deg[id] = INF;
            update(id, INF, 1, n, 1);

            for(int j = head[id]; j != -1; j = e[j].next)
            {
                int v = e[j].v;
                deg[v]--;
                update(v, deg[v], 1, n, 1);
            }
        }
        for(int i = 0; i < ans.size(); i++)
        i != ans.size() - 1 ? printf("%d ", ans[i]) : printf("%d\n", ans[i]);
    }
    return 0;
}