【Java】 剑指offer(10) 旋转数组的最小数字

/**
 * 
 * @Description 旋转数组的最小数字
 *
 * @author yongh
 * @date 2018年9月14日 下午8:30:29
 */

// 题目：把一个数组最开始的若干个元素搬到数组的末尾，我们称之为数组的旋转。
// 输入一个递增排序的数组的一个旋转，输出旋转数组的最小元素。例如数组
// {3, 4, 5, 1, 2}为{1, 2, 3, 4, 5}的一个旋转，该数组的最小值为1。

public class MinNumberInRotatedArray {
	public int minNumberInRotateArray(int[] array) {
		if (array == null || array.length <= 0) // 空数组或null时返回0
			return 0;
		int low = 0;
		int high = array.length - 1;
		int mid = (low + high) / 2;
		//升序数组
		if (array[low] < array[high])
			return array[low];
		//中间数字与首尾数字相等
		if (array[mid] == array[high] && array[mid] == array[low]) {
			for (int i = 1; i <= high; i++) {
				if (array[i] < array[i - 1])
					return array[i];
			}
			return array[low];
		}
		//正常情况
		while (low < high) {
			if (high - low == 1)
				break;
			mid = (low + high) / 2;
			if (array[mid] <= array[high])
				high = mid;
			if (array[mid] > array[high])
				low = mid;
		}
		return array[high]; // 别错写成了return high; !!
	}

	// =======测试代码======
	public void test1() {
		int[] array = null;
		System.out.println("test1:" + minNumberInRotateArray(array));
	}

	public void test2() {
		int[] array = {};
		System.out.println("test2:" + minNumberInRotateArray(array));
	}

	public void test3() {
		int[] array = { 1 };
		System.out.println("test3:" + minNumberInRotateArray(array));
	}

	public void test4() {
		int[] array = { 1, 2, 3, 4, 5, 6 };
		System.out.println("test4:" + minNumberInRotateArray(array));
	}

	public void test5() {
		int[] array = { 2, 2, 2, 2, 1, 2 };
		System.out.println("test5:" + minNumberInRotateArray(array));
	}

	public void test6() {
		int[] array = { 2, 1, 2, 2, 2, 2 };
		System.out.println("test6:" + minNumberInRotateArray(array));
	}

	public void test7() {
		int[] array = { 6, 6, 8, 9, 10, 1, 2, 2, 3, 3, 4, 5, 6 };
		System.out.println("test7:" + minNumberInRotateArray(array));
	}

	public static void main(String[] args) {
		MinNumberInRotatedArray demo = new MinNumberInRotatedArray();
		demo.test1();
		demo.test2();
		demo.test3();
		demo.test4();
		demo.test5();
		demo.test6();
		demo.test7();
	}
}

public class Solution {
    public int minNumberInRotateArray(int [] array) {
        int low = 0 ; int high = array.length - 1;   
        while(low < high){
            int mid = low + (high - low) / 2;        
            if(array[mid] > array[high]){
                low = mid + 1;
            }else if(array[mid] == array[high]){
                high = high - 1;
            }else{
                high = mid;
            }   
        }
        return array[low];
    }
}