算法导论 第七章 随机快速排序

#include <iostream> #include <cstdlib> #include <time.h> using namespace std; void swap(int array[] , int i , int j) { if(i!=j) //This comparision is most important. { //Because function Partition always let its element exchang itself. array[i] = array[i]+array[j]; array[j] = array[i]-array[j]; array[i] = array[i]-array[j]; } } int Partition(int array[] , int begin , int end) { int sentinel = array[end]; int i = begin-1; for(int j=begin ; j<end ; j++) { if(array[j] <= sentinel) { i++; swap(array , i , j); } } swap(array , i+1 , end); return i+1; } int RandomizedPartition(int array[] , int begin , int end) { srand(time(0)); int i = rand()%(end-begin+1)+begin; swap(array , i , end); return Partition(array , begin , end); } void QuickSort(int array[] , int begin , int end) { int q; if(begin < end) { q = RandomizedPartition(array , begin , end); QuickSort(array , begin , q-1); QuickSort(array , q+1 , end); } } int main() { const int n = 100; int a[n]; srand(time(0)); for(int i=1 ; i<n ; i++) { a[i] = rand()%100; } for(int i=1 ; i<n ; i++) { cout << a[i] << ' '; } cout << endl; QuickSort(a , 1 , n-1); for(int i=1 ; i<n ; i++) { cout << a[i] << ' '; } cout << endl; return 0; }