Submission #240831

#TimeUsernameProblemLanguageResultExecution timeMemory
240831zoomswkArranging Shoes (IOI19_shoes)C++17
100 / 100
341 ms275704 KiB
#include "shoes.h"
#include <queue>
using namespace std;

int n;
int done[200005];
queue<int> occ[400005];
int t[400005];
int tmp[200005];

int qr(int l, int r){
	int res = 0;
	for(l+=n, r+=n; l<r; l>>=1, r>>=1){
		if(l&1) res += t[l++];
		if(r&1) res += t[--r];
	}
	return res;
}

void add(int pos){
	for(t[pos+=n]++; pos>1; pos>>=1) t[pos>>1] = t[pos]+t[pos^1];
}

long long count_swaps(std::vector<int> s) {
	n = (int)s.size();
	for(int i=0; i<n; i++) occ[s[i]+n/2].push(i);
	long long res = 0;
	for(int i=0, pairs_done=0; i<n; i++){
		if(done[i]) continue;
		occ[s[i]+n/2].pop();
		int pos = occ[-s[i]+n/2].front();
		occ[-s[i]+n/2].pop();
		res += pos-2*pairs_done+qr(pos, n);
		if(s[i] < 0) res--;
		add(pos);
		done[pos]++;
		pairs_done++;
	}
	return res;
}
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