二分查找算法

使用循環實現&使用遞歸實現

package com.pt.spring.learn.bean;

import java.util.ArrayDeque;
import java.util.Queue;

public class BinFind {
    public static void main(String[] args) {
        int[] array = new int[]{1, 2, 3, 4, 5, 7, 8, 9, 10};
        System.out.println(binFind(array, 0, 8, 8));
        System.out.println(binSearchLoop(array, 0, 8, 9));
    }

    public static int binSearchLoop(int[] array, int startIndex, int endIndex, int objectValue) {
        Queue<int[]> paramsQueue = new ArrayDeque<>();
        paramsQueue.add(new int[]{startIndex, endIndex});
        while (!paramsQueue.isEmpty()) {
            int[] tmpParams = paramsQueue.poll();
            startIndex = tmpParams[0];
            endIndex = tmpParams[1];
            if (objectValue > array[endIndex] || objectValue < array[startIndex] || startIndex > endIndex) {
                return -1;
            }
            if (startIndex == endIndex && array[endIndex] != objectValue) {
                return -1;
            }

            int mid = (startIndex + endIndex) / 2;
            if (array[mid] == objectValue) {
                return mid;
            }

            if (array[mid] > objectValue) {
                paramsQueue.add(new int[]{startIndex, mid});
            } else {
                paramsQueue.add(new int[]{mid + 1, endIndex});
            }
        }
        return -1;
    }

    public static int binFind(int[] array, int startIndex, int endIndex, int objectValue) {
        if (objectValue > array[endIndex] || objectValue < array[startIndex] || startIndex > endIndex) {
            return -1;
        }
        if (startIndex == endIndex && array[endIndex] != objectValue) {
            return -1;
        }

        int mid = (startIndex + endIndex) / 2;
        if (array[mid] == objectValue) {
            return mid;
        }

        if (array[mid] > objectValue) {
            return binFind(array, startIndex, mid, objectValue);
        } else {
            return binFind(array, mid + 1, endIndex, objectValue);
        }
    }


}

 

樹表查找，包括二叉搜索樹的構建與元素查找；

package com.pt.spring.learn.bean;

/**
 * 二叉查找樹：
 * 某節點若是左子樹不爲空，左子樹上全部節點的值都小於該節點的值
 * 若是右子樹不爲空，右子樹上全部節點的值都大於該節點的值
 * 左右子樹也都是二叉查找樹
 */
public class BinarySearchTree {
    public static void main(String[] args) {
        System.out.println("-----start run----");
        int[] array = new int[]{8, 6, 9, 7, 1, 3, 5};
        //構建二叉查找樹
        Node root = null;
        for (int i = 0; i < array.length; i++) {
            root = insert(root, array[i]);
        }
        System.out.println(root);

        //查找
        Node get = searchNode(root, 90);
        System.out.println(get);

    }

    static Node searchNode(Node root, int data) {
        if (root == null) {
            return null;
        }
        if (root.value == data) {
            return root;
        }

        if (root.value > data) {
            return searchNode(root.leftNode, data);
        } else {
            return searchNode(root.rightNode, data);
        }
    }

    static Node insert(Node root, int data) {
        if (root == null) {
            return new Node(data);
        }
        if (root.value >= data) {
            root.leftNode = insert(root.leftNode, data);
        } else {
            root.rightNode = insert(root.rightNode, data);
        }
        return root;
    }

    static class Node {
        Integer value;
        Node leftNode;
        Node rightNode;

        public Node(Integer value) {
            this.value = value;
        }

        @Override
        public String toString() {
            return "{" +
                    "\"value\":" + value +
                    ", \"leftNode\":" + leftNode +
                    ", \"rightNode\":" + rightNode +
                    '}';
        }
    }
}