Cod sursa(job #1982417)

Utilizator MaligMamaliga cu smantana Malig Data 18 mai 2017 18:35:00
Problema Statistici de ordine Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.19 kb
#include <iostream>
#include <fstream>
#include <math.h>
#include <algorithm>
#include <cstdlib>
#include <time.h>

using namespace std;
ifstream in("sdo.in");
ofstream out("sdo.out");

#define ll long long
#define pb push_back
const int NMax = 5e6 + 5;

int N,K;
int v[NMax];

void solve(int,int);
int part(int,int);

int main() {
    in>>N>>K;
    for (int i=1;i <= N;++i) {
        in>>v[i];
    }

    srand(time(0));
    solve(1,N);

    out<<v[K]<<'\n';

    in.close();out.close();
    return 0;
}

void solve(int st,int dr) {
    if (st >= dr) {
        return;
    }

    int idx = part(st,dr);
    if (K < idx) {
        solve(st,idx-1);
    }
    if (K > idx) {
        solve (idx+1,dr);
    }
}

int part(int st,int dr) {
    int idx = rand() % (dr-st+1) + st;
    swap(v[st],v[idx]);

    int i = st-1,
        j = dr+1;
    while (true) {
        do {
            ++i;
        }
        while (v[i] < v[st]);

        do {
            --j;
        }
        while (v[j] > v[st]);

        if (i < j) {
            swap(v[i],v[j]);
        }
        else {
            swap(v[st],v[j]);
            return j;
        }
    }
}