350. Intersection of Two Arrays II

Leetcode

https://leetcode.com/problems/intersection-of-two-arrays-ii/

題目

Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must appear as many times as it shows in both arrays and you may return the result in any order.

Example 1:

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]

Example 2:

Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]
Explanation: [9,4] is also accepted.

解答

• 方法一

利用 hash table 儲存 nums1 矩陣中已遍歷過的值，再遍歷 nums2 矩陣找出重複的數

var intersect = function(nums1, nums2) {
    const hash = {};
    
    for(let i=0; i<nums1.length; i++) {
        const value = nums1[i];
        if(!hash[value]) hash[value] = 1;
        else hash[value]++;
    }
    
    const arr = [];
    for(let i=0; i<nums2.length; i++) {
        const value = nums2[i];
        if(!hash[value]) continue;
        else {
            arr.push(value);
            hash[value]--;
        }
    }
    
    return arr;
};

Runtime: 80 ms, faster than 66.90% of JavaScript online submissions for Intersection of Two Arrays II.

Memory Usage: 40.8 MB, less than 43.90% of JavaScript online submissions for Intersection of Two Arrays II.

測資

let nums1 = [1,2,2,1], nums2 = [2,2]; // [2,2]
nums1 = [4,9,5], nums2 = [9,4,9,8,4]; // [4,9]

console.log(intersect(nums1, nums2))