Java review 003, java003
Today I will mainly review the data structure.
Tree
Red/black tree (symmetric Binary Tree B) (wiki)
Features:
Advantages:
Purpose: used to construct correlated arrays (Map) and sets)
B tree
B + tree
Feature: No data is saved for each keyword and is only used for indexing. All data is saved on the leaf node. if the search is successful, the process ends only when the query is successful on the leaf node (different from B-tree)
Purpose: it is usually used in file systems of databases and operating systems.
B * tree
B + tree variants add pointers to brothers in non-root and non-leaf nodes of B + tree; BThe number of non-leaf node keywords defined in the tree must be at least (2/3)M, that is, the minimum block usage is 2/3 (instead of 1/2 of B + tree );
Key tree
Trie tree (Dictionary tree)
A typical application is used for statistics, sorting, and saving a large number of strings (but not limited to strings). Therefore, it is often used by the search engine system for text word frequency statistics.
Advantage: the common prefix of the string is used to reduce the query time and minimize unnecessary string comparisons. The query efficiency is higher than that of the hash table.Sorting (implemented in java)
See my other blog: some-sort-algorithms
Binary Search
Package vell. bibi. algorithms. search;
Public class BinarySearch {
// Non-Recursive Implementation
Public static int search (int [] a, int key ){
Int low = 0, high = a. length-1, mid = 0;
While (high> = low ){
Mid = (high + low)/2;
If (key = a [mid]) return mid;
Else if (key> a [mid]) low = mid + 1;
Else high = mid-1;
}
Return-1;
}
// Recursive Implementation
Public static int search (int [] a, int low, int high, int key ){
If (high <low) return-1;
Int mid = (low + high)/2;
If (key = a [mid]) return mid;
Else if (key> a [mid]) return search (a, mid + 1, high, key );
Else return search (a, low, mid-1, key );
}
Public static void main (String [] args ){
Int [] a = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
System. out. println (search (a, 5 ));
System. out. println (search (a, 0, a. length-1, 5 ));
}
}
Java end exam of Northeast Forestry University
Value: 0 = 0.
How to Implement output similar to 003 in java
Use a string
Int x;
String str = null;
If (x <10 ){
Str = "00" + x;
} Else if (x <100 ){
Str = "0" + x;
} Else {
Str = String. valueOf (x );
}
