循環有序數組，查找值

一、從一個循環有序數組總查找給定值

　　1、思路：先通過中間值和最后一個或者第一個元素比較，找出局部有序范圍，再通過二分查找局部有序段

　　

private static int sortArrFindOne(int arr[], int low, int high, int target) {
        int mid = (high - low) / 2 + low;
        if (arr[mid] == target) return mid;
        if (arr[mid] < arr[high]) {
            if (arr[mid] < target && target <= arr[high]) {
                return find(arr, mid, high, target);
            } else {
                return sortArrFindOne(arr, low, mid, target);
            }
        } else {
            if (arr[low] <= target && target < arr[mid]) {
                return find(arr, low, mid, target);
            } else {
                return sortArrFindOne(arr, mid, high, target);
            }
        }
    }

　　2、找局部有序（二分遞歸查找）

　　

//局部有序
    private static int find(int arr[], int low, int high, int target) {
        int mid = (high - low) / 2  + low;
        if (arr[mid] == target) return mid;
        if (arr[mid] < target) {
            return find(arr, mid + 1, high, target);
        } else {
            return find(arr, low, mid - 1, target);
        }
    }

　　3、測試

public static void main(String[] args) {
        int arr[] = {6, 7, 8, 9, 1, 2, 3, 4, 5};
        System.out.println(sortArrFindOne(arr, 0, arr.length - 1, 8));
        System.out.println(sortArrFindOne(arr, 0, arr.length - 1, 1));
        System.out.println(sortArrFindOne(arr, 0, arr.length - 1, 5));
        System.out.println(sortArrFindOne(arr, 0, arr.length - 1, 6));
    }