100-5

2019独角兽企业重金招聘Python工程师标准>>>

/*=================================================================*\
100-5:查找最小的k个元素

题目：输入n个整数，输出其中最小的k个。
例如输入1，2，3，4，5，6，7和8这8个数字，则最小的4个数字为1，2，3和4。
\*=================================================================*/

#include <iostream>

#define N 9

using namespace std;

int partition(int *index,int begin,int end){
	int i = begin;
	int j = end;
	int temp;

	while (i < j)
	{
		while(index[i] < index[j]){
			--j;
		}
		if (i < j)
		{
			temp = index[i];
			index[i] = index[j];
			index[j] = temp;
		}
		while (index[i] < index[j])
		{
			++i;
		}
		if(i < j){
			temp = index[i];
			index[i] = index[j];
			index[j] = temp;
		}
	}
	return i;
}

void printIndex(int *index){
	for(int i = 0; i < N ; ++i){
		cout << index[i] << " ";
	}
	cout << endl;
}

void quickSort(int *index,int begin,int end){//快速排序
	if (begin < end)
	{
		int k = partition(index,begin,end);
		quickSort(index,begin,k);
		quickSort(index,k+1,end);
	}
}

int quickFind(int *index,int begin,int end,int i){//快速查找前i个元素
	if(begin < end){
		int k = partition(index,begin,end);
		//cout << i << "<" << k << ": ";
		//printIndex(index);
		int pIndex = k+1;
		if (i == pIndex){
			return k;
		}else if(i < pIndex){
			return quickFind(index,begin,k-1,i);
		}else if(i > pIndex){
			return quickFind(index,k+1,end,i);
		}
	}else if (begin == end){
		return begin;
	}
}

int main(){
	int index[N] = {2,6,1,3,5,9,7,8,4};//测试数据
	int k = quickFind(index,0,8,4);//找前4个小的数
	//cout << k << endl;
	for(int i = 0;i <= k ; ++i){
		cout << index[i] << " ";
	}
}

转载于:https://my.oschina.net/dapengking/blog/82923