Java Binary lookup-binary lookup algorithm

Two-point Search:

This algorithm is relatively simple and easy to understand. The algorithm is looking for an ordered array, so you want to use this algorithm

first, you want to sort the array.

There are actually three pointers, starting with the pointer, the end pointer, the middle pointer, to Start. Binary find.

The steps are as Follows:

1, determine three pointers, Start,end,middleindex.

2, the judgment start<=end, if satisfies, executes this method, does not satisfy, returns, cannot find.

3, in the premise of 2, we find its binary, middleindex = Start+end >> 1, take the middle Value.

4. Determine if the value of the middle position is equal to the target value, and return to this position if it is equal.

unequal, if the value of the middle position is larger than the target value, the array in the left half is recursively looking for the target value,

otherwise, the array on the right looks for the recursive target Value.

5. Return Value.

package com.test4;/** *  binary search  *  *  @author  sdc * */public  class BinarySearch {//  the number of times an element needs to be found static int count;public static void  main (string[] args)  {}/** *  binary lookup--recursive form, binary lookup is an ordered array lookup  *  * @ param sortarray *  @param  start *  @param  end *  @param  target  *  @return  */public static int binarysearch (int[] sortarray, int  Start, int end, int target)  {if  (sortarray == null)  {return  -1;} int sortarraylength = sortarray.length;if  (sortarraylength == 1)  {return  sortarray[0];} count++;//  really started, find if  (start <= end)  {//  Middle position int middleindex =   (start + end)  >> 1;//  Median value int middledata = sortarray[ Middleindex];if  (middledata == target)  {return middleindex;}  else if  (middledata < target)  {return binarysearch (sortarray,  middleindex + 1, end, target);}  else {return binarysearch (sortarray, start, middleindex - 1, target);}} The return value given by  else { //  is not return -1;}} /** *  binary search-non-recursive form  *  *  @param  sortArray *  @param  target  *  @return  */public static int serarch (int[] sortarray, int  Target)  {if  (sortarray == null)  {return -1;}   Start position int start = 0;//  End position int end = sortarray.length - 1; while  (start <= end)  { //  always loops to find//  middle position int middleindex =  (start + end)  >> 1;if (sortarray[middleindex] == target) &nbsP {return middleindex;} Else if (sortarray[middleindex] > target)  {end = middleindex -1;} else {start = middleindex +1;}} return -1;}}

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Java Binary lookup-binary lookup algorithm