Question

下面的随机选择程序没有找到第i个统计数据。以下程序遵循Cormen的算法简介中提供的算法。提前感谢您找到错误。

#include<stdio.h>
#include<stdlib.h>
int random(int a,int b) //generates random numbers [a,b]
{
    return a+(rand()%(b-a+1));
}
void swap(int *a,int *b) //swwaps the elements
{
    int temp;
    temp=*a;
    *a=*b;
    *b=temp;
}
int partition(int a[],int p,int r) //partitioning similar to that of quicksort
{
    int i=p-1,j,x=a[r];
    for(j=p;j<r;j++)
    {
        if(a[i]<x)
        {
            i++;
            swap(&a[i],&a[j]);
        }
    }
    swap(&a[i+1],&a[r]);
    return i+1;
}
int random_partition(int a[],int p,int r) //random index generation whose element gets swapped with the last element of the array
{
    int q=random(p,r);
    swap(&a[q],&a[r]);
    return partition(a,p,r);
}
int random_selection(int a[],int p,int r,int index) //finds the i'th order statistic
{
    if(p==r)
    return a[p];
    if(p<r)
    {
        int mid,k;
        mid=random_partition(a,p,r);
        k=mid-p+1;
        if(k==index)
        return a[mid];
        if(index<k)
        return random_selection(a,p,mid-1,index);
        if(index>k)
        return random_selection(a,mid+1,r,index);
    }
}
main()
{
    int a[50],i,size,index;
    printf("enter the size of the array\n");
    scanf("%d",&size);
    printf("enter the array elements\n"); //takes array elements input
    for(i=1;i<=size;i++)
    {
        scanf("%d",&a[i]);
    }
    for(i=1;i<=size;i++) //prints the index of each element
    {
    printf("%d\n",random_selection(a,1,size,i));
}
}

Answer 1

您的srand()需要main()吗？就像这些线程一样 Recommended way to initialize srand? 和How does srand relate to rand function?

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main()
{
   int i, n;
   time_t t;

   n = 5;

   /* Intializes random number generator */
   srand((unsigned) time(&t));

   /* Print 5 random numbers from 0 to 50 */
   for( i = 0 ; i < n ; i++ ) 
   {
      printf("%d\n", rand() % 50);
   }

   return(0);
}

随机选择-i＆＃39;顺序统计

1 个答案: