#include <iostream>
#include <vector>
#include <set>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <stdio.h>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <complex>
#include <stack>
#include <set>
#define FOR(i,n) for(int i=0;i<n;i++)
#define FORE(i,a,b) for(int i=a;i<=b;i++)
#define ll long long int
#define vi vector<int>
#define ii pair<ll,ll>
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define pll pair<ll,ll>
#define cd complex<double>
const int INF = 1e9;
using namespace std;
const int MAXN = 4000*4000+500;
vector<ii> g[MAXN];
char grid[4000][4000];
int n,m;
inline int cost(char c1,char c2){
return (c1 == '.' or c2 == '.')?-1:(1-(c1==c2));
}
int dist[MAXN];
bool vis[MAXN];
inline int change(int i,int j){
return i*m+j;
}
inline void insertEdge(int a,int b,int c,vector<ii>& v){
v.pb({b,c});
}
inline void getEdges(int i,int j,vector<ii>& v){
if(i > 0 and cost(grid[i][j],grid[i-1][j])>=0){
insertEdge(change(i,j),change(i-1,j),cost(grid[i][j],grid[i-1][j]),v);
}
if(j > 0 and cost(grid[i][j],grid[i][j-1])>=0){
insertEdge(change(i,j),change(i,j-1),cost(grid[i][j],grid[i][j-1]),v);
}
if(i < n-1 and cost(grid[i][j],grid[i+1][j])>=0){
insertEdge(change(i,j),change(i+1,j),cost(grid[i][j],grid[i+1][j]),v);
}
if(j < m-1 and cost(grid[i][j],grid[i][j+1])>=0){
insertEdge(change(i,j),change(i,j+1),cost(grid[i][j],grid[i][j+1]),v);
}
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
FOR(i,n){
cin >> s;
FOR(j,m)grid[i][j] = s[j];
}
/*
FOR(i,n){
FOR(j,m){
if(i > 0 and cost(grid[i][j],grid[i-1][j])>=0){
insertEdge(change(i,j),change(i-1,j),cost(grid[i][j],grid[i-1][j]));
}
if(j > 0 and cost(grid[i][j],grid[i][j-1])>=0){
insertEdge(change(i,j),change(i,j-1),cost(grid[i][j],grid[i][j-1]));
}
if(i < n-1 and cost(grid[i][j],grid[i+1][j])>=0){
insertEdge(change(i,j),change(i+1,j),cost(grid[i][j],grid[i+1][j]));
}
if(j < m-1 and cost(grid[i][j],grid[i][j+1])>=0){
insertEdge(change(i,j),change(i,j+1),cost(grid[i][j],grid[i][j+1]));
}
}
}*/
FOR(i,MAXN)dist[i] = INF;
queue<ii> q1;
queue<ii> q2;
q1.push({0,0});
while(1){
if(q1.empty() and q2.empty())break;
if(q1.empty())swap(q1,q2);
auto e = q1.front();q1.pop();
if(vis[e.ss])continue;
vis[e.ss] = 1;
dist[e.ss] = e.ff;
vector<ii> v;
//getEdges(e.ss/m,e.ss%m,v);
int i = e.ss/m;
int j = e.ss%m;
if(i > 0 and cost(grid[i][j],grid[i-1][j])>=0){
//insertEdge(change(i,j),change(i-1,j),cost(grid[i][j],grid[i-1][j]),v);
v.pb({(i-1)*m+j,cost(grid[i][j],grid[i-1][j])});
}
if(j > 0 and cost(grid[i][j],grid[i][j-1])>=0){
v.pb({(i)*m+j-1,cost(grid[i][j],grid[i][j-1])});
//insertEdge(change(i,j),change(i,j-1),cost(grid[i][j],grid[i][j-1]),v);
}
if(i < n-1 and cost(grid[i][j],grid[i+1][j])>=0){
v.pb({(i+1)*m+j,cost(grid[i][j],grid[i+1][j])});
//insertEdge(change(i,j),change(i+1,j),cost(grid[i][j],grid[i+1][j]),v);
}
if(j < m-1 and cost(grid[i][j],grid[i][j+1])>=0){
v.pb({(i)*m+j+1,cost(grid[i][j],grid[i][j+1])});
//insertEdge(change(i,j),change(i,j+1),cost(grid[i][j],grid[i][j+1]),v);
}
for(auto f : v){
if(dist[f.ff] <= dist[e.ss]+f.ss)continue;
if(f.ss == 0){
q1.push({e.ff,f.ff});
}else{
q2.push({e.ff+1,f.ff});
}
//pq.push({dist[e.ss]+f.ss,f.ff});
}
}
//return 0;
int mx = 0;
FOR(i,n){
FOR(j,m){
if(grid[i][j] != '.'){
mx = max(mx,dist[change(i,j)]);
}
// cout << setw(10) <<dist[change(i,j)] << " ";
}
//cout << endl;
}
cout << (mx + 1) << endl;
return 0;
}
Compilation message
tracks.cpp: In function 'int main()':
tracks.cpp:72:10: error: 's' was not declared in this scope
cin >> s;
^
