剑指Offer - 旋转数组的最小数字

//C++ 二分法
class Solution {
public:
    int minNumberInRotateArray(vector<int> rotateArray) {
        if (rotateArray.empty()) return 0;
        int left = 0, right = rotateArray.size() - 1;
        while (left < right) {
            //确认子数组是否是类似1,1,2,4,5,..,7的非递减数组
            if (rotateArray[left] < rotateArray[right]) return rotateArray[left];
             
            int mid = left + (right - left) / 2;
            //左半数组为有序数组，旋转部分在右半数组
            if (rotateArray[left] < rotateArray[mid])
                left = mid + 1;
            //旋转部分在左半数组,右半数组为有序数组
            else if (rotateArray[left]>rotateArray[mid])
                right = mid;
            //否则rotateArray[left] == rotateArray[mid] 
            //出现这种情况的array类似[1,0,1,1,1] 或者[1,1,1,0,1]，
            //此时最小数字不好判断在mid左边还是右边,只好一个一个试
            else {
                left++;
            }
        }
        return rotateArray[left];
    }
};