给定一个无序数组，找到其中最小的K个数

/**
* 给定一个无序数组，找到其中最小的K个数
* @author Administrator
*
*/
public class getMinKNum {
public static void main(String[] args) {

}//利用最大堆public static int[] getMinKNumByHeap(int[]arr ,int k){    if(arr==null ||arr.length<k|| k<0){        return null;    }    int[] kHeap = new int[k];    for(int i =0 ; i<k; i++){        heapInsert(kHeap,arr[i],i);    }    for(int i=k; i<arr.length; i++){        if(kHeap[0]>arr[i]){            kHeap[0] = arr[i];            heapify(kHeap, 0, k);        }    }    return kHeap;} //建堆的过程public static void heapInsert(int[] heap, int value, int index){    heap[index] = value;    int parent = (index-1)/2;    while(index!=0){        if(heap[index]>heap[parent]){            swap(heap,index,parent);            index = parent;        }else{            break;        }    }}//调整的过程public static void heapify(int[] heap, int index, int heapSize){    int left = 2*index +1;    int right = 2*index +2;    int largest = index;    while(left < heapSize){        if(heap[index]<heap[left]){            //swap(heap,index,left);            largest = left;        }        if(right < heapSize && heap[largest]<heap[right]){            largest = right;        }        if(index!=largest){            swap(heap,index,largest);        }else{            break;        }        index = largest;        left = 2*index +1;        right = 2*index +2;    }}public static void swap(int[] arr, int low, int high){    int temp = arr[low];    arr[low] = arr[high];    arr[high] = temp;}public static int partition(int[] arr,int start,int end){    if(arr==null || arr.length==0){        return -1;     }    int l = start;    int r = end;    int temp = arr[l];    if(l<r){        while(l<r && temp >= arr[r]){            r--;        }        if(l<r){            arr[l++]=arr[r];        }        while(l<r && temp < arr[l]){            l++;        }        if(l<r){            arr[r--] = arr[l];        }    }    arr[l] = temp;    return l;}//利用快排思想public static void getKNum(int[] arr,int start,int end, int k){    int index = partition(arr, start, end);    while(index != k-1){        if(index < k-1){            index = partition(arr, index+1, end);        }else if(index > k-1){            index = partition(arr, start, index-1);        }else{            return;        }    }}

}