演算法-->折半查詢（快排）

package 折半查詢;

import java.util.Scanner;

public class ZheBan {
    static final int N = 15;

    static void quick(int[] arr, int left, int right) {
        int f, t;
        int rtemp, ltemp;
        ltemp = left;
        rtemp = right;
        f = arr[(rtemp + ltemp) / 2];// 確定分界值
        while (ltemp < rtemp) {
            while (arr[ltemp] < f) {
                ++ltemp;
            }
            while (arr[rtemp] > f) {
                --rtemp;
            }
            if (ltemp <= rtemp) {
                t = arr[ltemp];
                arr[ltemp] = arr[rtemp];
                arr[rtemp] = t;
                --rtemp;
                ++ltemp;
            }
        }
        if (ltemp == rtemp) {
            ltemp++;

        }
        if (left < rtemp) {
            quick(arr, left, ltemp - 1);
        }
        if (ltemp < right) {
            quick(arr, rtemp + 1, right);
        }
    }

    static int search(int a[], int n, int x) {
        int low, mid, hight;
        low = 0;
        hight = n - 1;
        while (low <= hight) {
            mid = (low + hight) / 2;
            if (a[mid] == x) {
                return mid;
            } else if (a[mid] > x) {
                hight = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        return -1;
    }

    public static void main(String[] args) {
        ZheBan bb = new ZheBan();
        int[] shuzu = new int[N];
        int x, i, n;
        for (i = 0; i < N; i++) {
            shuzu[i] = (int) (100 + Math.random() * (100 + 1));
        }
        System.out.print("折半查詢演算法演示\n");
        System.out.print("排序前資料序列：\n");
        for (i = 0; i < N; i++) {
            System.out.print(" " + shuzu[i]);
        }
        System.out.print("\n\n");
        quick(shuzu, 0, N - 1);
        System.out.print("排序後的資料序列：\n");
        for (i = 0; i < N; i++) {
            System.out.print(" " + shuzu[i]);
        }
        System.out.print("\n\n");
        System.out.print("輸入要查詢的數：");
        Scanner sc = new Scanner(System.in);
        x = sc.nextInt();
        n = search(shuzu, N, x);
        if (n < 0) {
            System.out.println("沒找到資料" + x);
        } else {
            System.out.println("資料" + x + "位於陣列的第" + (n + 1) + " 個元素處");
        }

    }
}