Submission #583861

#	Time	Username	Problem	Language	Result	Execution time	Memory
583861		M_W	Sorting (IOI15_sorting)	C++17	36 / 100	13 ms	468 KiB

sorting

#include <bits/stdc++.h>
#define ii pair<int, int>
using namespace std;
int S[200002];
int gp = 0, pa[200002], from[200002], aa[200002];
bool vis[200002];

int findpa(int a){
	return pa[a] == a ? a : findpa(pa[a]);
}

int findSwapPairs(int N, int S_tmp[], int M, int X[], int Y[], int P[], int Q[]) {
    for(int i = 0; i < N; i++){
    	S[i] = S_tmp[i]; pa[i] = -1;
	}
    for(int i = 0; i < N; i++){
    	if(vis[i]) continue;
    	int cur = i;
    	while(!vis[cur]){
    		vis[cur] = true;
    		cur = S[cur];
		}
		gp++;
	}
	
	// Already sorted
	if(N == gp){
		P[0] = 0; Q[0] = 0;
		return 0;
	}
	// Nah
	for(int k = 0; k < N; k++){
		swap(S[X[k]], S[Y[k]]);
		
		gp = 0;
		for(int i = 0; i < N; i++) vis[i] = false;
		for(int i = 0; i < N; i++){
	    	if(vis[i]) continue;
	    	int cur = i;
	    	while(!vis[cur]){
	    		vis[cur] = true;
	    		from[S[cur]] = cur;
	    		cur = S[cur];
			}
			gp++;
		}
		
		if(N - k - 1 <= gp){
			queue<ii> q;
			for(int i = 0; i < N; i++) vis[i] = false;
			for(int i = 0; i < N; i++){
				if(vis[i]) continue;
				int cur = from[i]; vis[i] = true;
				while(!vis[cur]){
					vis[cur] = true;
					q.push({i, cur});
					cur = from[cur];
				}
			}
			
			for(int i = 0; i < N; i++) aa[i] = i;
			for(int j = k; j >= 0; j--){
				if(q.empty()) P[j] = Q[j] = 0;
				else{
					auto [u, v] = q.front();
					q.pop();
					
					P[j] = aa[u];
					Q[j] = aa[v];
					swap(aa[X[j]], aa[Y[j]]);
				}
			}
			
			return k + 1;
		}
	}
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:12:43: warning: unused parameter 'M' [-Wunused-parameter]
   12 | int findSwapPairs(int N, int S_tmp[], int M, int X[], int Y[], int P[], int Q[]) {
      |                                       ~~~~^
sorting.cpp:77:1: warning: control reaches end of non-void function [-Wreturn-type]
   77 | }
      | ^

• Subtask 1: 8 / 8
• Subtask 2: 12 / 12
• Subtask 3: 16 / 16
• Subtask 4: 0 / 18
• Subtask 5: 0 / 20
• Subtask 6: 0 / 26