算法导论 思考题 9-1

#include <stdio.h>#include <stdlib.h>#include <limits.h>#define LEN 20typedef struct heapType{int *a;int heapLen;}heap,*heapPtr;void swop(int *a,int *b){int temp=*a;*a=*b;*b=temp;}int partition(int a[],int p,int r){int i=p-1,x=a[r],j;for(j=p;j<r;j++){if(a[j]>x){i++;swop(&a[j],&a[i]);}}swop(&a[r],&a[i+1]);return i+1;}int at(int a[],int p,int r,int i){if(p==r)return a[p];int q=partition(a,p,r);int k=q-p+1;if(i==k)return a[q];else if(i<k)return at(a,p,q-1,i);elsereturn at(a,q+1,r,i-k);}void heapMaxify(heapPtr hp,int i){int max=hp->a[i],maxi=i;int l=hp->a[2*i],r=hp->a[2*i+1];if(2*i<=hp->heapLen && l>max){maxi=2*i;max=l;}if(2*i+1<=hp->heapLen && r>max){maxi=2*i+1;max=r;}swop(&hp->a[i],&hp->a[maxi]);if(maxi != i)heapMaxify(hp,maxi);}heapPtr buildHeap(int a[],int len){heapPtr hp=(heapPtr)malloc(sizeof(heap));hp->a=a;hp->heapLen=len;for(int i=len/2;i>=1;i--){heapMaxify(hp,i);}return hp;}int extractMax(heapPtr hp){if(hp->heapLen<1)return INT_MIN;int r=hp->a[1];hp->a[1]=hp->a[hp->heapLen];hp->heapLen--;heapMaxify(hp,1);return r;}void heapSort(heapPtr hp){}void printA(int a[],int p,int r){for(int i=p;i<=r;i++){printf("%d ",a[i]);}printf("\n");}int main(){int a[10]={INT_MIN,98,23,2,11,6,24,76,84,55};int k=5;int max;heapPtr hp=buildHeap(a,9);/*at(a,1,9,k);//a.前k个最大的数int index=partition(a,1,9);printA(a,1,k);for(int i=1;i<=k;i++){max=extractMax(hp);printf("%d ",max);}//b.建立一个最大优先队列，并调用extract-max过程k次printf("\n");*/int *b=(int*)malloc((k+1)*sizeof(int));b[0]=INT_MIN;at(a,1,9,k);for(int i=1;i<=k;i++){max=extractMax(hp);b[i]=max;}//c.利用顺序统计量算法找第k大元素，再对前i大的数排序printA(b,1,k);getchar();}