Submission #151669

#	Time	Username	Problem	Language	Result	Execution time	Memory
151669		ae04071	Arranging Shoes (IOI19_shoes)	C++14	100 / 100	530 ms	22912 KiB

shoes

#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;
using lli = long long;
using pii = pair<int,int>;

int n;
struct seg_tr{
    int tr[200001];
    void init() {
        for(int i=0;i<=n;i++) tr[i] = 0;
    }
    void upd(int cur, int val) {
        while(cur<=n) tr[cur]+=val, cur+=cur&-cur;
    }
    int get(int cur) {
        int ret=0;
        while(cur) ret+=tr[cur], cur-=cur&-cur;
        return ret;
    }
}seg;
long long count_swaps(vector<int> s) {
    set<pii> vi, iv;
    n = s.size();
    seg.init();
    for(int i=0;i<s.size();i++) {
        vi.insert({s[i], i});
        iv.insert({i, s[i]});
        seg.upd(i+1, 1);
    }
    
    lli ans = 0;
    int n=s.size() / 2;
    for(int i=0;i<n;i++) {
        auto st = iv.begin();
        auto mat = vi.lower_bound({-st->se, 0});
        ans += seg.get(mat->se);
        if(st->se < 0) ans--;
        
        seg.upd(st->fi+1, -1);
        seg.upd(mat->se+1, -1);
        iv.erase({mat->se, -st->se});
        vi.erase(mat);
        vi.erase({st->se, st->fi});
        iv.erase(st);
    }
    return ans;
}

Compilation message (stderr)

shoes.cpp: In function 'long long int count_swaps(std::vector<int>)':
shoes.cpp:27:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<s.size();i++) {
                 ~^~~~~~~~~

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