數據結構-02 數組(有序數組) -二分法查找(折半查找)

1、主方法當然實現的方式還有遞歸等)

/**
	 * 二分法查找
	 */
	public int binarySearch(long value){
		int middle = 0;	//中間的值爲0
		int low = 0;	//最左邊
		int pow = elements;	//最右的
		
		if(value<arr[low] || value>arr[pow-1]) return -1;
		
		while(true){
			middle = (low + pow) / 2;
			if(arr[middle] == value)
				return middle;
			else if(low > pow)
				return -1;
			else {
				if(arr[middle] > value){	//往左查找
					pow = middle - 1;
				}else{	//向右查詢
					low = middle + 1;
				}
			}
			
		}
	}

2、整體代碼：

package org.gzw.arr;

public class MyOrderArray {
	private long[] arr; 
	/* 有效數據的長度 */
	private int elements;

	public MyOrderArray() {
		arr = new long[50];
	}

	public MyOrderArray(int maxSize) {
		arr = new long[maxSize];
	}
	
	/**
	 * 添加數據(在此排序:從小到大)
	 */
	public void insert(long value){
		int i;
		for(i=0;i<elements;i++){
			if(arr[i] > value) 
				break;
		}
		//從後向前
		for(int j=elements;j>i;j--){
			arr[j] = arr[j-1];
		}
		arr[i] = value;
		elements++;
		
	}
	
	/**
	 * 顯示數據
	 */
	public String display(){
		StringBuffer strbuf = new StringBuffer();
		strbuf.append("[ ");
		/*for(long l : arr){
			strbuf.append(l + ", ");
		}*/
		for(int i =0; i<elements;i++){
			strbuf.append(arr[i] + ", ");
		}
		strbuf.delete(strbuf.length()-1, strbuf.length());
		strbuf.append("]");
		return strbuf.toString();
	}
	
	/**
	 * 二分法查找
	 */
	public int binarySearch(long value){
		int middle = 0;	//中間的值爲0
		int low = 0;	//最左邊
		int pow = elements;	//最右的
		
		if(value<arr[low] || value>arr[pow-1]) return -1;
		
		while(true){
			middle = (low + pow) / 2;
			if(arr[middle] == value)
				return middle;
			else if(low > pow)
				return -1;
			else {
				if(arr[middle] > value){	//往左查找
					pow = middle - 1;
				}else{	//向右查詢
					low = middle + 1;
				}
			}
			
		}
	}
	
	/**
	 * 查詢數據，並返回位置索引
	 */
	public int search(long value){
		int i;
		for(i=0;i<elements;i++){
			if(arr[i] == value) break;
		}
		
		if(i==elements){
			return -1;
		}else{
			return i;
		}
	}
	
	/**
	 * 查找數據，更具索引來查
	 */
	public long get(int index){
		if(0<=index && index<elements){
			return arr[index]; 
		}else{
			throw new ArrayIndexOutOfBoundsException();
		}
	}
	
	/**
	 * 刪除數據
	 */
	public void delete(int index){
		if(0<=index && index<elements){
			for(int i=index;i<elements;i++){
				if(i<elements-1){
					arr[i] = arr[i+1];
				}else break;
				
			}
			elements--;
		}else{
			throw new ArrayIndexOutOfBoundsException();
		}
	}
	
	/**
	 * 更新數據
	 */
	public void change(int index, long value){
		if(0<=index && index<elements){
			arr[index] = value;
		}else{
			throw new ArrayIndexOutOfBoundsException();
		}
	}
}

3、測試

package org.gzw.arr;

public class TestMyOrderArray {
	
	public static void main(String[] args) {
		MyOrderArray myOrderArr = new MyOrderArray(6);
		myOrderArr.insert(1);
		myOrderArr.insert(139);
		myOrderArr.insert(229);
		myOrderArr.insert(9);
		myOrderArr.insert(19);
		myOrderArr.insert(39);
		System.out.println(myOrderArr.display());
		
		System.out.println(myOrderArr.binarySearch(139));

	}
}

4、運行結果：

[ 1, 9, 19, 39, 139, 229,]
4