/*
Code by @marlov
*/
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <utility>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <stack>
#include <queue>
#include <iterator>
#include <bitset>
using namespace std;
typedef long long ll;
typedef pair<long long,long long> ii;
#define maxN 1000005
#define INF 1000000000
long long N;
bool visited[maxN];
vector<ll> child;
long long root;
long long cg=-1;
long long td[maxN];
long long mr[maxN];
vector<vector<ll> > grps;
void dfs(long long n){
if(visited[n]) return;
visited[n]=true;
grps.back().push_back(n);
td[cg]+=abs(n-child[n]);
long long tr=n-root;
if(abs(tr)<abs(mr[cg])) mr[cg]=tr;
dfs(child[n]);
}
ll minimum_walk(vector<ll> p, ll s){
N=p.size();
child=p;
root=s;
fill(mr,mr+maxN,INF);
for(long long i=0;i<N;i++){
if(!visited[i]){
cg++;
grps.push_back(vector<ll>());
dfs(i);
}
}
long long result=0;
long long ld=s;
long long rd=s;
for(long long i=0;i<=cg;i++){
if(grps[i].size()==1) continue;
result+=td[i];
if(mr[i]<=0) ld=min(ld,mr[i]);
if(mr[i]>=0) rd=max(rd,mr[i]);
}
return result+2*(rd-ld);
}
/*
long long main() {
ios_base::sync_with_stdio(0); cin.tie(0);
cout<<minimum_walk({0,2,3,1},0);
return 0;
}
*/
/* stuff you should look for
* long long overflow, array bounds
* special cases (n=1,n=0?)
* do smth instead of nothing and stay organized
*/
Compilation message
/tmp/ccIPkUOi.o: In function `main':
grader.cpp:(.text.startup+0x211): undefined reference to `minimum_walk(std::vector<int, std::allocator<int> >, int)'
collect2: error: ld returned 1 exit status
