This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#pragma GCC optimize ("O3")
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define int short
int n;int m;
//int dis[30100];
vector<int>e[30100];
set<int>st[30100];
//map<pair<int,int>,int>vis;
//map<pair<int,int>,int>dis;
gp_hash_table<int, signed> dis[30010];
//gp_hash_table<int, bool> vis[30100];
bitset<30010>vis[30100];
int ar[30100];
//int frm[30100];
signed main(){
cin.tie(0);
ios_base::sync_with_stdio(0);
cin>>n>>m;
for(int i=0;i<m;i++){int v;
cin>>ar[i]>>v;
st[ar[i]].insert(v);
// e[ar[i]].push_back(br[i]);
}
for(int i=0;i<n;i++){
for(auto it=st[i].begin();it!=st[i].end();it++){
e[i].push_back(*it);
}
// e[i].push_back(0);
}
dis[ar[0]][0]=1;
deque<pair<int,int>>dq;
dq.push_back({ar[0],0});
//int cnt=0;
while(dq.size()){
int nw=dq.front().first;
int nwd=dq.front().second;
// cnt++;
assert(dis[nw][nwd]<=30010);
dq.pop_front();
if(vis[nw][nwd]){continue;}
vis[nw][nwd]=1;
if(nw==ar[1]){
cout<<dis[nw][nwd]-1<<endl;return 0;
}
if(nwd==0){
for(int i=0;i<e[nw].size();i++){
int d=e[nw][i];
if(vis[nw][d]){continue;}
if(dis[nw][d]==0){
dis[nw][d]=dis[nw][nwd];
dq.push_front({nw,d});
continue;
}
if(dis[nw][d]>dis[nw][nwd]){
dis[nw][d]=dis[nw][nwd];
dq.push_front({nw,d});
}
}e[nw].clear();
// continue;
}else{
int d=0;
if(!vis[nw][d]){
if(dis[nw][d]==0){
dis[nw][d]=dis[nw][nwd];
dq.push_front({nw,d});
// continue;
}else{
if(dis[nw][d]>dis[nw][nwd]){
dis[nw][d]=dis[nw][nwd];
dq.push_front({nw,d});
}}
}
}
if(nwd==0){continue;}
if(((int)nw+(int)nwd)<(int)n){
if(!vis[nw+nwd][nwd]){
if(dis[nw+nwd][nwd]==0){
dis[nw+nwd][nwd]=dis[nw][nwd]+1;
dq.push_back({nw+nwd,nwd});
//continue;
}else{
if(dis[nw+nwd][nwd]>dis[nw][nwd]+1){
dis[nw+nwd][nwd]=dis[nw][nwd]+1;
dq.push_back({nw+nwd,nwd});
}}
}
}
if((int)nw-nwd>=0){
if(!vis[nw-nwd][nwd]){
if(dis[nw-nwd][nwd]==0){
dis[nw-nwd][nwd]=dis[nw][nwd]+1;
dq.push_back({nw-nwd,nwd});
// continue;
}else{
if(dis[nw-nwd][nwd]>dis[nw][nwd]+1){
dis[nw-nwd][nwd]=dis[nw][nwd]+1;
dq.push_back({nw-nwd,nwd});
}}
}
}
}
cout<<dis[ar[1]][0]-1;
}
Compilation message (stderr)
skyscraper.cpp: In function 'int main()':
skyscraper.cpp:52:18: warning: comparison of integer expressions of different signedness: 'short int' and 'std::vector<short int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
52 | for(int i=0;i<e[nw].size();i++){
| ~^~~~~~~~~~~~~
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