LeetCode 1512. Number of Good Pairs

題目

Input: nums = [1,2,3,1,1,3]
Output: 4
Explanation: There are 4 good pairs (0,3), (0,4), (3,4), (2,5) 0-indexed.

解法思維

想到跑雙迴圈判斷

var numIdenticalPairs = function(nums) {
    let counter = 0;
    for (let i = 0; i < nums.length; i++) {
        for (let j = i+1; j < nums.length; j++) {
            if(nums[i]===nums[j]){
                counter++
            }
            
        }
    }
    return counter
};

利用for of

var numIdenticalPairs = function(nums) {
    let obj = {};
    let counter = 0;

    for (val of nums) {
        if (obj[val]) {
            counter += obj[val];
            obj[val]++;
        } else {
            obj[val] = 1;
        }
    }
    console.log(obj);
    return counter;
};

JS-for…in與for…of的差別