Submission #295682

#	Time	Username	Problem	Language	Result	Execution time	Memory
295682		tzero	Arranging Shoes (IOI19_shoes)	C++14	10 / 100	125 ms	38572 KiB

shoes

#include <iostream>
#include <vector>
#include <math.h>
#include <cassert>
#include <cstring>
using namespace std;
using ll = long long;
const int maxn = (int)1e5 + 7;
int t[8 * maxn], lz[8 * maxn];
int n;

void update(int v, int tl, int tr, int l, int r) {
  if(tl > r || tr < l) {
    return;
  } else if(tl >= l && tr <= r) {
    lz[v]++;
  } else {
    int tm = (tl + tr) / 2;
    update(2 * v, tl, tm, l, r);
    update(2 * v + 1, tm + 1, tr, l, r); 
  }
}

int query(int v, int tl, int tr, int i) {
  if(tl > i || tr < i) {
    return -1;
  }
  if(lz[v] > 0) {
    t[v] += lz[v];
    if(tl != tr) {
      lz[2 * v] += lz[v];
      lz[2 * v + 1] += lz[v];
    }
    lz[v] = 0;
  }
  if(tl == tr) {
    return t[v];
  } else {
    int tm = (tl + tr) / 2;
    int ans = query(2 * v, tl, tm, i); 
    if(ans != -1) return ans;
    ans = query(2 * v + 1, tm + 1, tr, i);
    return ans;
  }
}

ll count_swaps(vector<int> s) {
  n = (int)s.size();

  bool same_size = true;
  for(int i = 0; i < n; i++) {
    if(i > 0 && abs(s[i]) != abs(s[i - 1])) same_size = false;
  }

  memset(t, 0, sizeof(t));
  memset(lz, 0, sizeof(lz));

  vector<vector<int> > positions(n + 100);

  for(int i = 0; i < n; i++) {
    positions[s[i] + (n / 2)].push_back(i); 
  }

  int ans = 0;

  for(int position = n - 1; position >= 1; position -= 2) {
    int right_idx = position + query(1, 0, n - 1, position);
    int inverted_number = -s[right_idx] + (n / 2);

    // if(positions[inverted_number].size() == 0) assert(false); 

    int left_idx = positions[inverted_number].back();

    assert(s[right_idx] + s[left_idx] == 0);

    int closest = left_idx - query(1, 0, n - 1, left_idx);

    ans += position - closest;
    if(s[right_idx] > 0) ans--;

    positions[s[right_idx] + (n / 2)].pop_back();
    positions[-s[right_idx] + (n / 2)].pop_back(); 

    update(1, 0, n - 1, left_idx, position); 
  }

  return ans;
}

int _main() {
  int n;
  scanf("%d", &n);

  vector<int> _s(2 * n);
  for(int i = 0; i < 2 * n; i++) {
    scanf("%d", &_s[i]);
  }

  printf("%lld\n", count_swaps(_s));

  return 0;
}

Compilation message (stderr)

shoes.cpp: In function 'll count_swaps(std::vector<int>)':
shoes.cpp:50:8: warning: variable 'same_size' set but not used [-Wunused-but-set-variable]
   50 |   bool same_size = true;
      |        ^~~~~~~~~
shoes.cpp: In function 'int _main()':
shoes.cpp:92:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   92 |   scanf("%d", &n);
      |   ~~~~~^~~~~~~~~~
shoes.cpp:96:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   96 |     scanf("%d", &_s[i]);
      |     ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 15