#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e9+7;
const ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ll,ii>
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
#include "sorting.h"
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
int n = N;
if(is_sorted(S,S+N)){
return 0;
}
ll l = 1,r = m;
ll ans = m;
while(l <= r){
ll mid = (l+r)/2;
int cur[n];
int fin[n];
int pos[n],post[n];
f(i,0,n){
pos[S[i]] = i;
}
f(i,0,n){
cur[i] = S[i];
fin[i] = S[i];
}
f(j,0,mid){
swap(fin[X[j]],fin[Y[j]]);
}
f(i,0,n){
post[fin[i]] = i;
}
ll po = 0;
f(j,0,mid){
swap(pos[cur[X[j]]],pos[cur[Y[j]]]);
swap(cur[X[j]],cur[Y[j]]);
while(po < n && fin[po] == po){
po++;
}
if(po < n){
ll xx = pos[po],yy = pos[fin[po]];
swap(pos[cur[xx]],pos[cur[yy]]);
swap(cur[xx],cur[yy]);
xx = post[po],yy = post[fin[po]];
swap(post[fin[xx]],post[fin[yy]]);
swap(fin[xx],fin[yy]);
}
}
while(po < n && fin[po] == po){
po++;
}
if(pos == n){
r = mid - 1;
ans = min(ans,mid);
}
else{
l = mid + 1;
}
}
int cur[n];
int fin[n];
int pos[n],post[n];
f(i,0,n){
pos[S[i]] = i;
}
f(i,0,n){
cur[i] = S[i];
fin[i] = S[i];
}
f(j,0,ans){
swap(fin[X[j]],fin[Y[j]]);
}
f(i,0,n){
post[fin[i]] = i;
}
ll po = 0;
f(j,0,ans){
swap(pos[cur[X[j]]],pos[cur[Y[j]]]);
swap(cur[X[j]],cur[Y[j]]);
while(po < n && fin[po] == po){
po++;
}
if(po < n){
ll xx = pos[po],yy = pos[fin[po]];
P[j] = xx,Q[j] = yy;
swap(pos[cur[xx]],pos[cur[yy]]);
swap(cur[xx],cur[yy]);
xx = post[po],yy = post[fin[po]];
swap(post[fin[xx]],post[fin[yy]]);
swap(fin[xx],fin[yy]);
}
else{
P[j] = Q[j] = 0;
}
}
return ans;
}
Compilation message
sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:31:18: error: 'm' was not declared in this scope
31 | ll l = 1,r = m;
| ^
sorting.cpp:39:25: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
39 | pos[S[i]] = i;
| ^
sorting.cpp:49:28: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
49 | post[fin[i]] = i;
| ^
sorting.cpp:70:16: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
70 | if(pos == n){
| ~~~~^~~~
sorting.cpp:82:21: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
82 | pos[S[i]] = i;
| ^
sorting.cpp:92:24: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
92 | post[fin[i]] = i;
| ^
sorting.cpp:103:20: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
103 | P[j] = xx,Q[j] = yy;
| ^~
sorting.cpp:103:30: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
103 | P[j] = xx,Q[j] = yy;
| ^~
sorting.cpp:114:9: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
114 | return ans;
| ^~~
sorting.cpp:26:39: warning: unused parameter 'M' [-Wunused-parameter]
26 | int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
| ~~~~^
