153.FindMin.cs

// 153. Find Minimum in Rotated Sorted Array
// Suppose an array of length n sorted in ascending order is rotated between 1 and n times. For example, the array
// nums = [0,1,2,4,5,6,7] might become:
// [4,5,6,7,0,1,2] if it was rotated 4 times.
// [0,1,2,4,5,6,7] if it was rotated 7 times.
// Notice that rotating an array [a[0], a[1], a[2], ..., a[n-1]] 1 time results in the array
// [a[n-1], a[0], a[1], a[2], ..., a[n-2]].
// Given the sorted rotated array nums of unique elements, return the minimum element of this array.
// You must write an algorithm that runs in O(log n) time.
// Example 1:
// Input: nums = [3,4,5,1,2]
// Output: 1
// Explanation: The original array was [1,2,3,4,5] rotated 3 times.
// Example 2:
// Input: nums = [4,5,6,7,0,1,2]
// Output: 0
// Explanation: The original array was [0,1,2,4,5,6,7] and it was rotated 4 times.
// Example 3:
// Input: nums = [11,13,15,17]
// Output: 11
// Explanation: The original array was [11,13,15,17] and it was rotated 4 times. 

public class Solution {
    public int FindMin(int[] nums) {
        int left = 0,
            right = nums.Length-1;
        while(left < right){
            if(nums[left] < nums[right])
                return nums[left];
            int mid = (right - left)/2 + left;
            if(nums[mid] < nums[left])
                right = mid;
            else
                left = mid+1;
        }
        return nums[left];
    }
}