Cod sursa(job #1976155)

Utilizator BogdanisarBurcea Bogdan Madalin Bogdanisar Data 2 mai 2017 20:43:21
Problema Radix Sort Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.78 kb
#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
#include <algorithm>

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

#define pb push_back
#define ll long long
const int NMax = 1e7 + 5;
const int nrBytes = 4;
const int Radix = 0xFF;

// Algoritmul Radix Sort

ll N,A,B,C;
int v1[NMax],v2[NMax];
// v1,v2 - vectori din care se copiaza elementele in celalalt la fiecare ordonare counting sort

void countingSort(int*,int*,int);

int main() {
    in>>N>>A>>B>>C;
    v1[1] = B;

    A %= C;
    B %= C;
    // se genereaza vectorul input
    for (int i=2;i <= N;++i) {
        v1[i] = (A * v1[i-1] + B) % C;
    }

    for (int i=1;i <= nrBytes;++i) {
        if (i & 1) {
            countingSort(v1,v2,i-1);
        }
        else {
            countingSort(v2,v1,i-1);
        }
    }

    // elementele vor fi in v1 deoarece countingSort se apeleaza cu un i par ultima oara
    for (int i=1;i <= N;i += 10) {
        out<<v1[i]<<' ';
    }

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

// se foloseste algoritmul Counting Sort pentru fiecare byte al unui numar
// (fiecare int va avea 4 bytes);
// se sorteaza elementele din vectorul one,
// dupa bit-ii corespunzatori byte-ului (bytes+1) (de la dreapta la stanga)
// si se vor pune in vectorul two
void countingSort(int* one,int* two,int bytes) {
    #define nrBits 8
    int occ[(1<<nrBits) + 5] = {};

    for (int i=1;i <= N;++i) {
        ++occ[(one[i]>>(bytes * nrBits)) & Radix];
    }

    int total = 0;
    for (int i=0;i <= Radix;++i) {
        int old = occ[i];
        occ[i] = total + 1;
        total += old;
    }

    for (int i=1;i <= N;++i) {
        two[occ[(one[i]>>(bytes * nrBits)) & Radix]++] = one[i];
    }
}