Submission #971383

#TimeUsernameProblemLanguageResultExecution timeMemory
971383happy_nodeMisspelling (JOI22_misspelling)C++17
29 / 100
802 ms266700 KiB
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

const int MX=5e5+5, mod=1e9+7;
int N,M;

vector<pair<int,int>> open[MX], close[MX];

ll dp[MX][26], sdp[MX][26];

int main() {
	cin.tie(0); ios_base::sync_with_stdio(0);

	cin>>N>>M;

	for(int i=0;i<M;i++) {
		int a,b;
		cin>>a>>b;

		if(a<b) {
			open[a].push_back({b,0}); // s_{i-1} > s{i}
			close[b].push_back({a,0});
		} else {
			// a > b
			open[b].push_back({a,1}); // s_{i-1} < s{i}
			close[a].push_back({b,1});
		}
	}

	for(int c=0;c<26;c++) dp[1][c]=1, sdp[1][c]=1;

	multiset<int> st[2];
	st[0].insert(0);
	st[1].insert(0);
	for(auto [j,t]:open[1]) st[t].insert(1);

	for(int i=2;i<=N;i++) {
		int p=*st[0].rbegin();
		int q=*st[1].rbegin();
		
		if(p<=q) {
			ll cur=0;
			for(int c=0;c<26;c++) {
				dp[i][c]+=cur;
				dp[i][c]%=mod;
				cur+=sdp[i-1][c];
				cur-=sdp[min(p,q)][c];
				cur+=mod;
				cur%=mod;
			}
		}

		if(p>=q) {
			ll cur=0;
			for(int c=25;c>=0;c--) {
				dp[i][c]+=cur;
				dp[i][c]%=mod;
				cur+=sdp[i-1][c];
				cur-=sdp[min(p,q)][c];
				cur+=mod;
				cur%=mod;
			}
		}

		for(int c=0;c<26;c++) {
			sdp[i][c]=sdp[i-1][c]+dp[i][c];
			sdp[i][c]%=mod;
		}
		
		for(auto [j,t]:open[i]) st[t].insert(i);
		for(auto [j,t]:close[i]) {
			st[t].erase(st[t].find(j));
		}
	}

	ll ans=0;
	for(int c=0;c<26;c++) {
		ans+=sdp[N][c];
		ans%=mod;
	}

	cout<<ans<<'\n';
}
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