Find-Minimum-in-rotated-sorted-array.js

/*
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. 

*/

var findMin = function (nums) {
	let res = nums[0];
	let [l, r] = [0, nums.length - 1];

	while (l <= r) {
		// if the array is sorted
		if (nums[l] < nums[r]) {
			res = Math.min(res, nums[l]);
			break;
		}

		// if array is not sorted
		let m = Math.floor((l + r) / 2);

		res = Math.min(res, nums[m]);

		if (nums[m] >= nums[l]) {
			l = m + 1;
		} else {
			r = m - 1;
		}
	}

	return res;
};