锦标赛排序之使用n+lgn-2次比较来选出第二小的元素

最新推荐文章于 2018-07-18 14:42:38 发布

Kontrol

最新推荐文章于 2018-07-18 14:42:38 发布

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分类专栏：每日算法文章标签： struct float input div

本文链接：https://blog.youkuaiyun.com/Kontrol/article/details/6870165

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本文介绍了一种算法，用于在未排序数组中找到第二小的元素，包括数据输入、数组排序过程及寻找第二小元素的方法。

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/*
* FindSecondElement.c
*
* Created on: 2011-10-13
*      Author: kontrol
*/

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

#define MAX 1000

struct Node
{
   int data;
   struct Node * lchild;
   struct Node * rchild;
   _Bool tag;
};

int upper(int n, int div) //求上整数
{
   float r = (float)n/div;
   if(r == n/div)
       return r;
   else return n/div + 1;
}

void findSecondElement(int a[], int length)
{
   struct Node* elements = (struct Node*)malloc(length * sizeof(struct Node));
   memset((void *)elements, 0 , length * sizeof(struct Node));
   int j = 0;
   while(j<length)
   {
       elements[j].data = a[j];
       j++;
   }
   struct Node * p = elements;
   int count = length;
   while(count > 0) //退出循环的条件比较难写
   {
       if(count == 1) break;
       int i = 0;
       struct Node* upperLayer = (struct Node *)malloc(upper(count, 2) * sizeof(struct Node));
       while(i+1<count)
       {
           if(p[i].data < p[i+1].data)
           {
               upperLayer[i/2].data = p[i].data;
               upperLayer[i/2].lchild = p + i;
               upperLayer[i/2].rchild = p+ i +1;
               upperLayer[i/2].tag = 1;
           }
           else
           {
               upperLayer[i/2].data = p[i+1].data;
               upperLayer[i/2].rchild = p + i + 1;
               upperLayer[i/2].lchild = p + i;
               upperLayer[i/2].tag = 0;
           }
           i += 2;
       }
       if(i+1 == count)//说明原来那一层是基数个元素
       {
           upperLayer[upper(count, 2)-1].data = p[i].data;
           upperLayer[upper(count, 2)-1].lchild = p + i;
           upperLayer[upper(count, 2)-1].rchild = 0;
           upperLayer[upper(count, 2)-1].tag = 1;
       }
       p = upperLayer;
       count = upper(count, 2);
   }
   printf("the minumin element is %d\n", p->data);
   printf("the second minumin element is: ");
   int secondMin = 0;
if (p->tag)
{
secondMin = p->rchild->data;
p = p->lchild;
}
else
{
secondMin = p->lchild->data;
p = p->rchild;
}
while(p->rchild && p->lchild)
{
if (p->tag)
{
if(p->rchild->data < secondMin )
secondMin = p->rchild->data;
p = p->lchild;
}
else
{
if(p->lchild->data < secondMin )
secondMin = p->lchild->data;
p = p->rchild;
}
}

printf("%d", secondMin);
}

int main()
{
   puts("please input the scale of data:");
   int length = 0;
   scanf("%d", &length);
   int* a = (int *)malloc(length * sizeof(int));
   srand(time(0));
    int i=0;
    puts("the array is:");
    for(;i<length;i++)
    {
        a[i] = rand()%MAX;
        printf("%d ", a[i]);
    }
    printf("\n");
    findSecondElement(a, length);
   return 0;
}