Submission #594898

#	Time	Username	Problem	Language	Result	Execution time	Memory
594898		penguinhacker	Swapping Cities (APIO20_swap)	C++17	6 / 100	321 ms	39988 KiB

swap

#include "swap.h"
#include <bits/stdc++.h>
using namespace std;

#define ar array

const int mxN=1e5, mxM=2e5;
int n, m, p[2*mxN], anc[2*mxN][18], first[2*mxN], n2, d[2*mxN], ew[2*mxN], epa[2*mxN], epb[2*mxN];
ar<int, 3> e[mxM];
vector<int> adj[2*mxN];

int find(int i) {
	return i^p[i]?p[i]=find(p[i]):i;
}

void dfs(int u) {
	for (int v : adj[u]) {
		d[v]=d[u]+1;
		if (ew[u]!=-1&&(ew[v]==-1||ew[u]<ew[v]))
			ew[v]=ew[u];
		dfs(v);
	}
}

void init(int N, int M, vector<int> U, vector<int> V, vector<int> W) {
	n=N, m=M, n2=n;
	for (int i=0; i<m; ++i)
		e[i]={W[i], U[i], V[i]};
	sort(e, e+m);
	iota(p, p+2*n, 0);
	memset(anc, -1, sizeof(anc));
	memset(first, -1, sizeof(first));
	for (int i=0; i<n; ++i)
		epa[i]=epb[i]=i;
	for (int i=0; i<m; ++i) {
		int u=find(e[i][1]), v=find(e[i][2]);
		if (u!=v) {
			p[u]=p[v]=anc[u][0]=anc[v][0]=n2;
			first[n2]=first[v]==-1||first[u]!=-1&&first[u]<first[v]?first[u]:first[v];
			if (first[n2]==-1) {
				if (epa[u]!=e[i][1]&&epb[u]!=e[i][1]&&epa[v]!=e[i][2]&&epb[v]!=e[i][2])
					first[n2]=e[i][0];
				else {
					epa[n2]=epa[u]^epb[u]^e[i][1];
					epb[n2]=epa[v]^epb[v]^e[i][2];
				}
			}
			ew[n2]=e[i][0];
			adj[n2].push_back(u);
			adj[n2].push_back(v);
			++n2;
		} else if (first[u]==-1)
			first[u]=e[i][0];
	}
	assert(n2==2*n-1);
	for (int j=1; j<18; ++j)
		for (int i=0; i<n2; ++i)
			anc[i][j]=anc[i][j-1]^-1?anc[anc[i][j-1]][j-1]:-1;
	for (int i=n; i<n2; ++i) {
		ew[i]=first[i]^-1?max(ew[i], first[i]):-1;
		//cout << i << " " << ew[i] << endl;
	}
	dfs(n2-1);
	//for (int i=n; i<n2; ++i)
	//	cout << i << " " << ew[i] << endl;
}

int lca(int u, int v) {
	if (d[u]>d[v])
		swap(u, v);
	for (int i=17; ~i; --i)
		if (d[v]-(1<<i)>=d[u])
			v=anc[v][i];
	if (u==v)
		return u;
	for (int i=17; ~i; --i)
		if (anc[u][i]!=anc[v][i])
			u=anc[u][i], v=anc[v][i];
	return anc[u][0];
}

int getMinimumFuelCapacity(int u, int v) {
	return ew[lca(u, v)];
}

Compilation message (stderr)

swap.cpp: In function 'void init(int, int, std::vector<int>, std::vector<int>, std::vector<int>)':
swap.cpp:39:40: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   39 |    first[n2]=first[v]==-1||first[u]!=-1&&first[u]<first[v]?first[u]:first[v];
      |                            ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 0 / 7
• Subtask 3: 0 / 17
• Subtask 4: 0 / 20
• Subtask 5: 0 / 23
• Subtask 6: 0 / 27