劍指offer 面試題30 找出數組中最小的k個數

#include <iostream>
#include <time.h>
#include <stdlib.h>
using namespace std;
//******************************************************
void Swap(int *a,int *b){
	int tmp=*a;
	*a=*b;
	*b=tmp;
}
int RandomInRange(int start,int end){
	srand(time(NULL));
	return start+rand()%(end-start+1);
}
int partition(int *number,int length,int start,int end){
	//if(number==NULL||length<=0||start<0||end>length-1)
		//throw new std::exception("Invalid Input.");
	int index=RandomInRange(start,end);
	Swap(&number[index],&number[end]);
	int flag=start;
	for(int i=start;i<end;++i){
		if(number[i]<number[end]){
			if(i!=flag)
				Swap(&number[i],&number[flag]);
			flag++;
		}
	}
	Swap(&number[flag],&number[end]);
	return flag;
}
//*******************************************************
//solution1:use partition to narrow
void GetLeastNum(int *input,int n,int *output,int k){
	if(!input||!output||n<=0||k<=0||n<k)
		return;
	if(n==k){
		for(int i=0;i<k;++i){
		output[i]=input[i];
		}
		return;
	}
	int start=0,end=n-1;
	int index=partition(input,n,start,end);
	while(index!=k){
		if(index>k){
			end=index-1;
			index=partition(input,n,start,end);
		}
		else{
			start=index+1;
			index=partition(input,n,start,end);
		}
		
	}
	for(int i=0;i<k;++i){
		output[i]=input[i];
	}
}
//solution2:to be continued
int main(){
	int array[]={5,7,6,8,2,4,1,9,3};
	int k;
	cin>>k;
	int *least=new int [k];
	GetLeastNum(array,sizeof(array)/sizeof(*array),least,k);
	for(int i=0;i<k;++i){
		cout<<least[i]<<' ';
	}
	delete []least;
}