Submission #395385

#	Time	Username	Problem	Language	Result	Execution time	Memory
395385		rocks03	Sorting (IOI15_sorting)	C++14	20 / 100	4 ms	460 KiB

sorting

//#pragma GCC target("avx2")
//#pragma GCC optimization("O3")
//#pragma GCC optimization("unroll-loops")
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ff first
#define ss second
#define pb push_back
#define SZ(x) ((int)(x).size())
#define all(x) x.begin(), x.end()
#define rep(i, a, b) for(int i = (a); i < (b); i++)
#define per(i, a, b) for(int i = (a); i >= (b); i--)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]){
    vector<int> pos;
    set<int> st;
    auto random_sol = [&](){
        int ans = 0;
        while(SZ(st)){
            int i = X[ans], j = Y[ans];
            auto it = st.find(S[i]);
            if(it != st.end())
                st.erase(it);
            it = st.find(S[j]);
            if(it != st.end())
                st.erase(it);
            swap(pos[S[i]], pos[S[j]]);
            swap(S[i], S[j]);
            if(S[i] != i) st.insert(i);
            if(S[j] != j) st.insert(j);
            if(SZ(st) == 0){
                P[ans] = Q[ans++] = 0; break;
            }
            int x = rng() % N;
            it = st.lower_bound(x);
            if(it == st.end()) it--;
            x = *it;
            i = pos[x], j = x;
            it = st.find(S[i]);
            if(it != st.end())
                st.erase(it);
            it = st.find(S[j]);
            if(it != st.end())
                st.erase(it);
            swap(pos[S[i]], pos[S[j]]);
            swap(S[i], S[j]);
            if(S[i] != i) st.insert(i);
            if(S[j] != j) st.insert(j);
            P[ans] = i, Q[ans++] = j;
        }
        return ans;
    };
    while(true){
        pos = vector<int>(N);
        rep(i, 0, N) pos[S[i]] = i;
        st.clear();
        rep(i, 0, N){
            if(pos[i] != i) st.insert(i);
        }
        int ans = random_sol();
        if(ans != -1) return ans;
    }
}

Compilation message (stderr)

sorting.cpp: In lambda function:
sorting.cpp:36:31: warning: operation on 'ans' may be undefined [-Wsequence-point]
   36 |                 P[ans] = Q[ans++] = 0; break;
      |                            ~~~^~
sorting.cpp:36:31: warning: operation on 'ans' may be undefined [-Wsequence-point]
sorting.cpp:38:27: warning: conversion from 'std::mersenne_twister_engine<long unsigned int, 32, 624, 397, 31, 2567483615, 11, 4294967295, 7, 2636928640, 15, 4022730752, 18, 1812433253>::result_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   38 |             int x = rng() % N;
      |                     ~~~~~~^~~
sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:18:39: warning: unused parameter 'M' [-Wunused-parameter]
   18 | int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]){
      |                                   ~~~~^

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