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33. Search in Rotated Sorted Array.js
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33. Search in Rotated Sorted Array.js
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/*
There is an integer array nums sorted in ascending order (with distinct values).
Prior to being passed to your function, nums is possibly rotated at an unknown pivot index k (1 <= k < nums.length) such that the resulting array is [nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]] (0-indexed). For example, [0,1,2,4,5,6,7] might be rotated at pivot index 3 and become [4,5,6,7,0,1,2].
Given the array nums after the possible rotation and an integer target, return the index of target if it is in nums, or -1 if it is not in nums.
You must write an algorithm with O(log n) runtime complexity.
Example 1:
Input: nums = [4,5,6,7,0,1,2], target = 0
Output: 4
Example 2:
Input: nums = [4,5,6,7,0,1,2], target = 3
Output: -1
Example 3:
Input: nums = [1], target = 0
Output: -1
Constraints:
1 <= nums.length <= 5000
-104 <= nums[i] <= 104
All values of nums are unique.
nums is an ascending array that is possibly rotated.
-104 <= target <= 104
*/
/**
* @param {number[]} nums
* @param {number} target
* @return {number}
*/
var search = function(nums, target) {
if (nums[0] === target) { return 0; }
if (nums.at(-1) === target) { return nums.length - 1; }
const pivotAt = findPivot(nums);
console.log('pivot=', pivotAt, 'pivotVal', nums[pivotAt]);
if (pivotAt === -1) { return searchBinary(nums, target); }
if (nums[pivotAt] === target) { return pivotAt; }
if (nums[0] <= target && target <= nums[pivotAt - 1]) {
// search [0...pivot]
return searchBinary(nums.slice(0, pivotAt), target);
}
// search [pivot...n]
const result = searchBinary(nums.slice(pivotAt), target);
return result >= 0 ? result + pivotAt : -1;
};
const searchBinary = (nums, val) => {
console.log('searchBinary', nums, val);
const _search = (nums, left, right) => {
const mid = left + Math.floor((right - left) / 2);
if (left > right) {
return -1;
}
if (nums[mid] === val) { return mid; }
if (val < nums[mid]) {
return _search(nums, left, mid - 1);
}
return _search(nums, mid + 1, right);
}
return _search(nums, 0, nums.length - 1);
}
const findPivot = (nums) => {
const _search = (nums, left, right) => {
if (left === right) { return left; }
if (left > right) { return -1; }
const mid = left + Math.floor((right - left) / 2);
if (nums[mid] > nums[mid + 1]) { return mid + 1; }
if (nums[mid - 1] > nums[mid] && nums[mid] < nums[mid + 1]) { return mid; }
if (nums[mid] > nums[right]) {
return _search(nums, mid + 1, right);
}
return _search(nums, left, mid - 1);
}
return _search(nums, 0, nums.length - 1);
}