#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
//#include<bits/extc++.h>
//__gnu_pbds
const int MOD = 1000000007;
const int N = 5e5+5;
ll dp[N][26][2][2];
bool start[N][2];
int inr[N][2];
int main(){
ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
int n,m;cin>>n>>m;
for(int i=0;i<m;i++){
int a,b;cin>>a>>b;
bool w=0;
if(a>b) {w=1; swap(a,b);}
start[a+1][w]=1;
inr[a+1][w]++;
inr[b+1][w]--;
}
for(int i=1;i<=n;i++){
inr[i][0]+=inr[i-1][0];
inr[i][1]+=inr[i-1][1];
}
for(int i=0;i<26;i++) dp[1][i][0][0]=1;
for(int i=2;i<=n;i++){
for(int c= 0;c<26;c++){
// cout<<(char)(c+'a')<<":";
for(int f=0;f<2;f++){
for(int s=0;s<2;s++){
int l[2][2];
int r[2][2];
for(int ff=0;ff<2;ff++){
for(int ss=0;ss<2;ss++){
l[ff][ss]=0;
r[ff][ss]=25;
}
}
// stupid trans
if(start[i][0]){
if(f){
l[0][0]=c;
r[0][0]=c;
l[1][0]=c;
r[1][0]=c;
}else{
l[0][0] = 0;
r[0][0] = c-1;
l[1][0] = 0;
r[1][0] = c-1;
}
}else if(inr[i][0]){
if(f){
l[0][0] = -1;
r[0][0] = -1;
l[1][0] = c;
r[1][0] = c;
}else{
l[0][0] = 0;
r[0][0] = 25;
l[1][0] = 0;
r[1][0] = c-1;
}
}else{
if(f){
l[0][0] = -1;
r[0][0] = -1;
l[1][0] = -1;
r[1][0] = -1;
}else{
l[0][0] = 0;
r[0][0] = 25;
l[1][0] = 0;
r[1][0] = 25;
}
}
if(start[i][1]){
if(s){
l[0][1]=c;
r[0][1]=c;
l[1][1]=c;
r[1][1]=c;
}else{
l[0][1] = c+1;
r[0][1] = 25;
l[1][1] = c+1;
r[1][1] = 25;
}
}else if(inr[i][1]){
if(s){
l[0][1] = -1;
r[0][1] = -1;
l[1][1] = c;
r[1][1] = c;
}else{
l[0][1] = 0;
r[0][1] = 25;
l[1][1] = c+1;
r[1][1] = 25;
}
}else{
if(s){
l[0][1] = -1;
r[0][1] = -1;
l[1][1] = -1;
r[1][1] = -1;
}else{
l[0][1] = 0;
r[0][1] = 25;
l[1][1] = 0;
r[1][1] = 25;
}
}
// stupid trans
for(int ff=0;ff<2;ff++){
for(int ss=0;ss<2;ss++){
int tl = max(l[ff][0],l[ss][1]);
int tr = min(r[ff][0],r[ss][1]);
if(tl>tr || tl<0 || tr<0) continue;
for(int cc=tl;cc<=tr;cc++){
dp[i][c][f][s] = (dp[i][c][f][s]+dp[i-1][cc][ff][ss])%MOD;
}
}
}
// cout<<dp[i][c][f][s]<<",";
}
}
//cout<<" ";
}
//cout<<"\n";
}
ll ans = 0;
for(int c=0;c<26;c++){
for(int f=0;f<2;f++){
for(int s=0;s<2;s++){
ans = (ans+dp[n][c][f][s])%MOD;
}
}
}
cout<<ans<<"\n";
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
4696 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
4444 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
4696 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
4444 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
4444 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
4444 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
4696 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
4444 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
4696 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
4444 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
