提出 #73369392

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ソースコード 拡げる

#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;

using ll = long long;
using ld = long double;
const ll mod = 998244353;
const ll MOD = 1000000007;
const ll INF = 2e9;
const ll LINF = 2e18;
const double PI=3.1415926535897932384626433832795028841971;

template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;


#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define chmax(x,y) x = max(x,y)
#define chmin(x,y) x = min(x,y)
#define yu_qurid(x,y) ((x)*(x)+(y)*(y))
#define OUT(x) cout << fixed << setprecision(15) << x << endl
#define BIT(n) (1LL << (n))
#define Yes cout<<"Yes"<<endl
#define No cout<<"No"<<endl
#define YN {cout<<"Yes"<<endl;}else{cout<<"No"<<endl;}

int dx[4] = {1,0,-1,0}; int dy[4] = {0,1,0,-1};

class UnionFind {
public:
	vector<int> par;

    UnionFind(int n) : par(n,-1){};

	void init(int sz) {
		par.assign(sz, -1);
	}
	int root(int pos) {
		if (par[pos] < 0) return pos;
		par[pos] = root(par[pos]);
		return par[pos];
	}
	bool unite(int u, int v) {
		u = root(u); v = root(v);
		if (u == v) return false;
		if(par[u] > par[v]) swap(u,v);
        par[u] += par[v];
        par[v] = u;
        return true;
	}
	bool same(int u, int v) {
		if (root(u) == root(v)) return true;
		return false;
	}

    int size(int x){
        return -par[root(x)];
    }
};


void solve(){
	ll n,m;
	cin >> n >> m;
	priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> pq;
	rep(i,m){
		int l,r;
		cin >> l >> r;
		pq.push(make_pair(l,r));
	}
	priority_queue<int,vector<int>,less<int>> pq2;
	ll cur = 0;
	ll cnt = 0;
	while(true){
		
		while(!pq.empty() && pq.top().first <= cur+1){
			pq2.push(pq.top().second);
			pq.pop();
		}
		if(pq2.empty()){
			cout << -1 << endl;
			return;
		}
		if(pq2.top() <= cur){
			cout << -1 << endl;
			return;
		}

		cur = pq2.top();
		pq2.pop();
		cnt++;
		if(cur >= n){
			break;
		}
	}
	cout << cnt << endl;
	return;
}

int main() {
	ios::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}

提出情報

ジャッジ結果