Find algorithm-binary lookup (also called binary search)

Brief introduction

Binary lookup (binary search), also known as binary search. The premise is that the records in the linear table must be order- critical , and the linear table must be stored sequentially .

Basic ideas

In an ordered table, the intermediate record is used as the comparison object, if the given value is equal to the key of the intermediate record, the search succeeds; If the given value is less than the middle record, the left half of the intermediate record continues to be searched, and if the given value is greater than the middle record, the right half of the middle record is searched. Repeat the process until the lookup succeeds, or if all lookup zones are not logged, the lookup fails.

Advantages and Disadvantages

1. Advantages

   Binary find, the advantages are less than the number of comparisons, Find Fast, average performance is good;

2. Disadvantages

   Requires the unknown origin table to be an ordered table, and the insertion and deletion difficulties. Therefore, the binary lookup method is suitable for an ordered list that does not change frequently and finds frequent.

Code implementation

public  int  binary _search  (int  [] arr, int  key) {int  Low = 0 ; int  high = Arr.length -1 ; int  mid; while  (Low <= High) {mid = (low + high)/2 ; if  (Key < Arr[mid]) {High = mid-1 ; } else  if  (Key > Arr[mid]) {low = mid + 1 ; } else  {return  mid; }} return -1 ; //table does not exist key } 

Find algorithm-binary lookup (also called binary lookup)