java commonly used algorithms

Selection sort, the complexity O (n²)

package com.example.demo;

import org.junit.Test;
/**
 * 选择排序
 * @author zhzh.yin
 *
 */
public class HTest {
	@Test
	public void testMethod(){
		Integer [] numList = {1,2,2,2,1,4,5,2,5,3,9,6};
		for(int i=0;i<numList.length-1;i++){
			int max = numList[i];
			for(int j = i+1;j<numList.length;j++){
				if(numList[i]<numList[j]){
					max = numList[j];
					numList[j]=numList[i];
					numList[i]=max;
				}
			}
		}
		for(int num:numList){
			System.out.print(numList[num]+" ");
		}
	}
}

　　

Bubble sort complexity O (nlogn)

package com.example.demo;

import org.junit.Test;
/**
 * 冒泡排序
 * @author zhzh.yin
 *
 */
public class FTest {
	@Test
	public void testMethod(){
		Integer[]numList = {1,2,1,1,1,8,3,5,1};
		if(numList.length==1){
			System.out.println("-1");
		}else if(numList.length==2){
			String string ="";
			System.out.println(
					numList[1]>numList[2]?
					numList[1]+""+numList[0]:numList.toString());;
		}
		int temp = 0;
		for(int i =0;i<numList.length-1;i++){
			for(int j=i+1;j<numList.length;j++){
				if(numList[i]<numList[j]){
					temp=numList[i];
					numList[i]=numList[j];
					numList[j]=temp;
				}
			}
		}
		for(int num :numList){
			System.out.print(num+" ");
		}
	}
}

　　

Dichotomy inquiry - non-iterative

org.junit.Test Import; 
/ ** 
 * locate the number N, a plurality of repeating applicable to digital, take up used portions of the native method integer math / rounding down 
 * middle = min + (max- min) / 2 algorithm is more accurate 
is not found * -1 
 * @author zhzh.yin 
 * 
 * / 
public class CTest { 
	@Test 
	public void testMethod () { 
		Integer [] = {1,2,3,3,3,4,5,5 NUM, } 5,5,5,6,6,6,7,10; 
		System.out.println ( "IS AT NUM The" + selectPosition (NUM,. 8)); 
	} 
	public int selectPosition (Integer [] numlist, NUM int ) { 
		int min = 0; 
		int = numList.length-max. 1; 
		int Middle = -1; 
		the while (min <= max) { 
			Middle = min + (max-min) / 2;  
			System.out.println ( "min to - "+ min +", max - "+ max +", middle - "+ middle);
			IF ((== Middle min || Middle == max) && numlist [Middle] = NUM) {! 
				Middle = -1;
				break;
			}
			if(numList[middle]<num){
				min=(int) Math.floor(middle);
			}else if(numList[middle]>num){
				max=(int) Math.ceil(middle);
			}else{
				break;
			}
		}
		return middle;
	}
}