Submission #1038304

#	Time	Username	Problem	Language	Result	Execution time	Memory
1038304		Ludissey	Fire (BOI24_fire)	C++17	100 / 100	597 ms	164608 KiB

Main

#include <bits/stdc++.h>
#define int long long
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
 
using namespace std;


struct node {
	int sum,index;
	node* left, *right;
	void update() {
		sum = max(left->sum,right->sum);
        if(left->sum > right->sum) index=left->index;
        else index=right->index;
 	}
    node(){
        sum=0;
        index=0;
        left=NULL;
        right=NULL;
    }
};


pair<int,int> query(node* root, int left, int right, int qLeft, int qRight) {
	if (left > qRight || right < qLeft) return {-1e9,-1};
	if (left >= qLeft && right <= qRight) return {root->sum, root->index};
	int mid = (left + right) / 2;
    pair<int,int> l=query(root->left, left, mid, qLeft, qRight);
    pair<int,int> r=query(root->right, mid + 1, right, qLeft, qRight);
    if(l.first>r.first) return l;
    else return r;
}

void build(node* root, int left, int right, const vector<pair<int,int>>& v) {
	if (left == right) {
		root->sum = v[left].first;
        root->index=v[left].second;
		return;
	}
	int mid = (left + right) / 2;
	root->left = new node();
	root->right = new node();
	build(root->left, left, mid, move(v));
	build(root->right, mid+1, right, move(v));
	root->update();
}
node* root;
vector<vector<int>> parent;
const int LOG=31;
vector<int> depth;
vector<int> tree;
bool lca(int a, int b){
    if(tree[a]!=tree[b]||depth[b]<depth[a]) return false;
    int d=depth[b]-depth[a];
    for (int j = LOG-1; j>=0; j--)
    {
        if(d&(1<<j)) b=parent[b][j];
    }
    return (a==b);
}
vector<pair<int,int>> a;
vector<vector<int>> child;
int n,m;
void dfs(int x, int d){
    depth[x]=d;
    for (auto u : child[x]) {
        tree[u]=tree[x];
        dfs(u,d+1);
    }
}

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(nullptr);
    cin >> n >> m;
    a.resize(n);
    depth.resize(n);
    tree.resize(n);
    parent.resize(n,vector<int>(LOG));
    child.resize(n);
    unordered_map<int,int> conv;
    set<int> cord;
    cord.insert(0);
    cord.insert(m);
    for (int i = 0; i < n; i++){
        cin >> a[i].first >> a[i].second;
        cord.insert(a[i].first);
        cord.insert(a[i].second);
        if(a[i].first>a[i].second) {
            a[i].second+=m;
            cord.insert(a[i].second);
        }
    }
    int x=0;
    for (auto u : cord)
    {
        conv[u]=x;
        x++;
    }
    vector<pair<int,int>> buildSEGTREE(x,{-1e9,-1});
    sort(a.begin(),a.end());
    for (int i = 0; i < n; i++) {
        if(buildSEGTREE[conv[a[i].first]].first<conv[a[i].second]){
            buildSEGTREE[conv[a[i].first]]={conv[a[i].second],i};
        }
    }
    root=new node();
    build(root, 0,x-1,move(buildSEGTREE));
    vector<int> roots;
    for (int i = 0; i < n; i++)
    {
        int p=query(root,0,x-1,conv[a[i].first],conv[a[i].second]).second;
        parent[i][0]=i;
        if(p>=0&&p!=i) {
            child[p].push_back(i);
            parent[i][0]=p;
        }
        else roots.push_back(i);
    }
    for (int j = 1; j < LOG; j++)
    {
        for (int i = 0; i < n; i++)
        {
            parent[i][j]=parent[parent[i][j-1]][j-1];
        }
    }
    
    for (int i = 0; i < sz(roots); i++){
        dfs(roots[i],0);
    }
    int mn=1e12;
    for (int i = 0; i < n; i++){
        if(a[i].second>=m){
            int p=query(root,0,x-1,conv[0],conv[(a[i].second-m)]).second;
            if(p==-1||i==p||!lca(i,p)) continue;
            mn=min(abs(depth[p]-depth[i])+1,mn);
        }
    }
    if(mn==1e12) mn=-1;
    cout << mn << "\n";
    return 0;
}
/*
10 240
3 68
7 126
40 121
58 152
73 139
89 166
121 197
126 311
212 271
237 350
*/

• Subtask 1: 14 / 14
• Subtask 2: 17 / 17
• Subtask 3: 9 / 9
• Subtask 4: 13 / 13
• Subtask 5: 21 / 21
• Subtask 6: 26 / 26