# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
793886 | Jarif_Rahman | Towns (IOI15_towns) | C++17 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include "sorting.h"
#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;
vector<pair<int, int>> get_swaps(vector<int> S){
int n = S.size();
vector<pair<int, int>> swaps;
vector<int> pos(n);
for(int i = 0; i < n; i++) pos[S[i]] = i;
vector<bool> bl(n, 0);
for(int i = 0; i < n; i++){
if(bl[S[i]]) continue;
if(S[i] == i){
bl[i] = 1;
continue;
}
int j = i;
while(1){
if(bl[S[j]]){
bl[j] = 1;
break;
}
swaps.pb({S[j], j});
bl[j] = 1;
j = S[j];
}
}
return swaps;
}
int findSwapPairs(int n, int S[], int m, int X[], int Y[], int P[], int Q[]){
bool sorted = 1;
for(int i = 0; i < n; i++) sorted&=(S[i] == i);
if(sorted) return 0;
int k;
vector<int> s(n);
for(int i = 0; i < n; i++) s[i] = S[i];
int a = 0, b = m-1;
int ls = -1;
while(a < b){
int md = (a+b)/2;
while(ls < md){
ls++;
swap(s[X[ls]], s[Y[ls]]);
}
while(ls > md){
swap(s[X[ls]], s[Y[ls]]);
ls--;
}
if(get_swaps(s).size() <= md+1) b = md;
else a = md+1;
}
k = a;
vector<int> pos(n);
for(int i = 0; i < n; i++) pos[S[i]] = i;
auto swaps = get_swaps(s);
for(int i = 0; i <= k; i++){
swap(S[X[i]], S[Y[i]]);
swap(pos[S[X[i]]], pos[S[Y[i]]]);
if(i >= swaps.size()) P[i] = 0, Q[i] = 0;
else{
auto [x, y] = swaps[i];
swap(pos[x], pos[y]);
swap(S[pos[x]], S[pos[y]]);
P[i] = pos[x], Q[i] = pos[y];
}
}
return k+1;
}