LeetCode & Binary Search 解题模版
In computer science, binary search, also known as half-interval search, logarithmic search, or binary chop, is a search algorithm that finds the position of a target value within a sorted array.
在计算机科学中，二分搜索（也称为半间隔搜索，对数搜索或二进制印章）是一种搜索算法，用于查找排序数组中目标值的位置。
Big O
Worst complexity: O(log n)
Average complexity: O(log n)
Best complexity: O(1)
Space complexity: O(1)
Data structure: Array
Class: Search algorithm
solutions
- 递归
- 迭代
leeetcode & binary-search
https://leetcode.com/problems/binary-search/
"use strict";
/**
*
* @author xgqfrms
* @license MIT
* @copyright xgqfrms
* @created 2020-07-30
* @modified
*
* @description 704. Binary Search
* @difficulty Easy
* @complexity O(n)
* @augments
* @example
* @link https://leetcode.com/problems/binary-search/
* @solutions
*
*/
const log = console.log;
/*
Example 1:
Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4
Example 2:
Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1
*/
/**
* @param {number[]} nums
* @param {number} target
* @return {number}
*/
var search = function(nums, target) {
let left = 0;
let right = nums.length - 1;
while (left <= right) {
// left + 差值
let mid = left + Math.floor((right - left) / 2);
// log(`mid`, nums[mid])
if(nums[mid] === target) {
// nums[mid] 值
return nums.indexOf(nums[mid]);
// return true;
} else if(nums[mid] > target) {
right = mid - 1;
} else {
left = mid + 1;
}
}
return -1;
// return false;
};
const test = search([-1,0,3,5,9,12], 9);
const test1 = search([-1,0,3,5,9,12], 2);
log(test)
log(test1)
// 4
// -1
best solution
https://leetcode.com/submissions/detail/374279676/
runtime
/**
* @param {number[]} nums
* @param {number} target
* @return {number}
*/
var search = function(nums, target) {
if(!nums.length) return -1
let start = 0, end = nums.length - 1
while(start <= end) {
if(nums[start] === target) return start
if(nums[end] === target) return end
let mid = Math.floor(start + (end - start) / 2)
if(nums[mid] === target) return mid
if(target > nums[mid]) {
start = mid + 1
} else {
end = mid - 1
}
}
return -1
};
Memory
/**
* @param {number[]} nums
* @param {number} target
* @return {number}
*/
var search = function(nums, target) {
let low = 0;
let high = nums.length -1;
while (low <= high) {
const mid = parseInt((low + high) / 2);
if (nums[mid] === target) {
return mid;
}
if (nums[mid] < target) {
low = mid + 1;
}
if (nums[mid] > target) {
high = mid - 1;
}
}
return -1;
}
refs
https://en.wikipedia.org/wiki/Binary_search_algorithm
https://www.youtube.com/results?search_query=binary+search+algorithm
https://www.youtube.com/watch?v=P3YID7liBug
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