面经，基础算法

喜欢ヅ旅行 2021-05-16 20:36 443阅读 0赞

### 目录 ###

*   *   *  1.排序
         *   *  1.冒泡排序
             *  2.快速排序

### 1.排序 ###

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#### 1.冒泡排序 ####

package sort; /** * Created by david on 2018/8/16 * 冒泡排序 */
    public class BubbleSort
     {     
     	private static int[] bubbleSort(int[] a)
     	 {        
    		 int len = a.length;        
     		for (int i = 1; i < len - 1; i++) 
     		{            
     			for (int j = 1; j < len - 1-i; j++)
     			 {                
      				if (a[j + 1] < a[j]) 
      				{                    
      					 swap(a, j + 1, j);               
      				 }         
        		   }       
            }      
    	return a;   
         //交换方法 
    	private static void swap(int[] a, int i, int j)
    	{         
    		int tmp = a[i];        
    		a[i] = a[j];       
    		a[j] = tmp;    
    	} 
    	//测试 
    	public static void main(String[] args)
    	{        
    		int[] a = { 1, 4, 6, 8, 99, 9, 2, 99};        
    		int[] sort = bubbleSort(a);       
       		for (int s : sort) 
    		{             
    			System.out.print(s + " ");       
         	   }      
    	}
    }

#### 2.快速排序 ####

package sort; /** * Created by david on 2018/8/16 * 快速排序 * 不稳定，时间复杂度 最理想 O(nlogn) * 最差时间O(n^2) */
    public class QuickSort 
    {     
    	private static int[] quickSort(int[] a, int low, int high)
    	{        
     		 //中心点 
     	 	int mid = 0;        
       	 	if (low < high)
        		{ 
        			id = partition(a, low, high);          
       	 		quickSort(a, low, mid - 1);          
        			quickSort(a, mid + 1, high);      
       		}       
        		return a;  
    	}
    	private static int partition(int[] a, int low, int high) 
    	{         
    		int b = a[low];       
    		while (low < high)
    		{            
    			while (low < high && a[high] >= b)
    			{                 
    				high--;            
    			}            
    			a[low] = a[high];            
    			while (low < high && a[low] <= b) 
    			{                 
    				low++;            
    			}            
    			a[high] = a[low];        
    		}        
    		a[low] = b;        
    		return low;    
    	}
    	//测试 
    	public static void main(String[] args) 
    	{         
    		int[] a = { 1, 14, 6, 8, 99, 9, 2, 99};        
    		int[] sort = quickSort(a, 0, 7);        
    		for (int s : sort) 
    		{             
    			System.out.print(s + " ");        
    		}    
    	}
    }

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