剑指offer java -查找旋转数组的最小数字

Posted 2020-09-30 在窗边的豆豆助

/**
 * Created by wqc on 2017/7/18.
 * 查找旋转数组的最小数字
 * 把一个数组最开始的若干个元素搬到数组的末尾，称为数组的旋转
 * 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
 * 如：3,4,5,1,2  为1,2,3,4,5的一个旋转，最小值为1
 */
public class Problem8_findMinNumber {
    public Integer findMinNum(int[] array)
    {
        if(array == null)
        {
            return null;
        }

        int leftIndex = 0;
        int rightIndex =array.length-1;
        int mid = 0;
        while(array[leftIndex]>=array[rightIndex])
        {
            if(rightIndex-leftIndex <= 1)
            {
                mid = rightIndex;
                break;
            }

            mid = (leftIndex + rightIndex)/2;
            if(array[leftIndex] == array[rightIndex] && array[leftIndex] == array[mid])
            {
                if(array[leftIndex + 1] != array[rightIndex - 1])
                {
                    mid = array[leftIndex + 1] < array[rightIndex -1] ? (leftIndex + 1) : (rightIndex - 1);
                    break;
                }else{
                    leftIndex++;
                    rightIndex--;
                }
            }else if(array[mid] >= array[leftIndex]){

                leftIndex = mid;
            }else if(array[mid] <= array[rightIndex]){

                rightIndex = mid;
            }
        }
        return array[mid];
    }

}