求数组中的K大数(时间复杂度控制…
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【源码】
package cn.edu.nwsuaf.cie.qhs;
import java.util.Random;
import java.util.Scanner;
public class GetGreateK {
private intinitArray[];
public int[]getInitArray() {
returninitArray;
}
public voidsetInitArray(int[] initArray) {
this.initArray = initArray;
}
publicGetGreateK(){}
publicGetGreateK(int[] array){
this.initArray = array;
}
public intrandom_partion(int start,int length){
Random rand= new Random();
int index =rand.nextInt(length);
int i =start-1;
int j =start;
this.swap(index, length-1);
for(j=start;j<length;j++){
if(initArray[j] < initArray[length-1]){
this.swap(++i, j);
}
}
this.swap(++i, length-1);
// System.out.println("------>"+i);
returni;
}
public intgetMaxK(int start,int length,int k){
intmid;
if(k<=0) return -1;
if(length<k) return -1;
mid =this.random_partion(start, length);
if (mid ==length-k) return initArray[mid];
else if(mid< length-k) returngetMaxK(start+mid+1,length-mid-1,k);
else returngetMaxK(start,mid,k-(length-mid));
}
public voidswap(int a,int b){
int temp =initArray[a];
initArray[a]= initArray[b];
initArray[b]= temp;
}
publicstatic void main(String[] args) {
// TODOAuto-generated method stub
//12012 3 945 965 66 232 65 7 8 898 56 878 170 13 5
package cn.edu.nwsuaf.cie.qhs;
import java.util.Random;
import java.util.Scanner;
public class GetGreateK {
//