이 제출은 이전 버전의 oj.uz에서 채점하였습니다. 현재는 제출 당시와는 다른 서버에서 채점을 하기 때문에, 다시 제출하면 결과가 달라질 수도 있습니다.
#include <iostream>
#include<bits/stdc++.h>
using namespace std;
const int N = 500005;
const int MOD = 1e9 + 7;
const int SIGMA = 26;
void add(int &x, long long y){
y%=MOD;
x += y;
if(x >= MOD)
x-=MOD;
if(x<0)
x+=MOD;
}
const int INF = -1e9;
struct aintstr{
vector<int> aint;
vector<int> lazy;
const static int SZ = N;
aintstr(): aint(4*N + 1, 0), lazy(4*N + 1, INF){
}
void propag(int nod, int l, int r){
if(lazy[nod] == INF)
return;
aint[nod] = 1LL * (r - l + 1) * lazy[nod] % MOD;
if(l != r){
lazy[2*nod] = lazy[2*nod + 1] = lazy[nod];
}
lazy[nod] = INF;
}
void update(int lpoz, int rpoz, int val, int nod = 1, int l = 1, int r = SZ){
propag(nod, l, r);
if(rpoz < l || lpoz >r)
return;
if(lpoz <= l && r <= rpoz){
lazy[nod] = val;
propag(nod, l, r);
return;
}
int mid = (l +r)/2;
update(lpoz, rpoz, val, 2*nod, l, mid);
update(lpoz, rpoz, val, 2*nod + 1, mid + 1, r);
aint[nod] = (aint[2*nod] + aint[2*nod + 1])%MOD;
}
int get_sum(){
propag(1, 1, SZ);
return aint[1];
}
};
int lessthan[N];
int bigthan[N];
int start[N][SIGMA + 1];
aintstr dp[SIGMA + 1][2]; /// 0 merge in jos, 1 merge in sus
int main()
{
int n, m;
cin>>n>>m;
for(int i = 1; i<=m; i++){
int x, y;
cin>>x>>y;
if(x < y)
bigthan[x] = max(bigthan[x], y);
if(x > y)
lessthan[y] = max(lessthan[y], x);;
}
for(int i = 1; i<=SIGMA; i++){
start[n][i] = 1;
}
for(int i = n - 1; i>=1; i--){
int total_sum = 0;
for(int let = 1; let<=SIGMA; let++){
dp[let][0].update(i + 1, i + 1, total_sum);
add(total_sum, start[i + 1][let]);
}
total_sum = 0;
for(int let = SIGMA; let>=1; let--){
dp[let][1].update(i + 1, i + 1, total_sum);
add(total_sum, start[i + 1][let]);
}
for(int let = 1; let<=SIGMA; let++){
if(bigthan[i]){
dp[let][0].update(i + 1, bigthan[i], 0);
}
if(lessthan[i]){
dp[let][1].update(i + 1, lessthan[i], 0);
}
start[i][let] = 1;
add(start[i][let], dp[let][0].get_sum());
add(start[i][let], dp[let][1].get_sum());
}
}
int ans = 0;
for(int i = 1; i<=SIGMA; i++)
add(ans, start[1][i]);
cout<<ans;
return 0;
}
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