省选模拟 19/10/07

Posted 2022-07-08 qq62c30ac77b2a7

​​CF793G Oleg and chess​​​ 首先暴力就是个二分图匹配，行向列连边
想到了线段树优化建图
于是有一种做法是先扫描线，然后每一列的线段树暴力连边
考虑到每一次只会有一段区间被修改，于是类似主席树一样
对于修改的节点我们行建一个点向下连边
然后就是 的模板

#include<bits/stdc++.h>
#define N 40050
#define M 4000050
using namespace std;
int read()
  int cnt = 0, f = 1; char ch = 0;
  while(!isdigit(ch)) ch = getchar(); if(ch == -) f = 0;
  while(isdigit(ch)) cnt = (cnt + (cnt << 2) << 1) + (ch ^ 48), ch = getchar();
  return f ? cnt : -cnt;

const int inf = 1e9;
struct opt int x, l, r, f;; 
vector<opt> v[N];
int n, m, st, ed, node;
int first[M], f2[M], nxt[M], to[M], w[M], tot = 1;
void add(int x, int y, int z)
  nxt[++tot] = first[x], first[x] = tot, to[tot] = y, w[tot] = z;
  nxt[++tot] = first[y], first[y] = tot, to[tot] = x, w[tot] = 0;

struct SGT
  int pos[M], cov[N];
  void pushup(int x)
    pos[x] = ++node; 
    if(!cov[x<<1]) add(pos[x], pos[x<<1], inf);
    if(!cov[x<<1|1]) add(pos[x], pos[x<<1|1], inf);
  
  void build(int x, int l, int r)
    if(l == r) pos[x] = n + l; return; 
    int mid = (l+r) >> 1; build(x<<1, l, mid); build(x<<1|1, mid+1, r);
    pushup(x);
  
  void modify(int x, int l, int r, int L, int R, int k)
    if(L<=l && r<=R) cov[x] += k; return; 
    int mid = (l+r) >> 1; 
    if(L<=mid) modify(x<<1, l, mid, L, R, k);
    if(R>mid) modify(x<<1|1, mid+1, r, L, R, k);
    pushup(x);
  
Seg;
int dis[M]; 
bool bfs()
  queue<int> q; q.push(st); 
  memset(dis, -1, sizeof(int)*(node+1)); dis[st] = 0;
  while(!q.empty())
    int x = q.front(); q.pop();
    for(int i = first[x]; i; i = nxt[i])
      int t = to[i]; if(w[i] && dis[省选模拟27

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