javascript – JSAlgorithm

Two Sum

Ronald — Mon, 11 May 2020 20:59:01 +0000

function twoSum(nums, target) {
    let result = [],
        cache = {};
    for (let i = 0; i < nums.length; i++) {
        let x = target - nums[i];
        if (cache[x] !== undefined) {
            result.push([cache[x], i]);
        }
        cache[nums[i]] = i;
    }

    return result;
};

Valid Parenthesis

Ronald — Mon, 11 May 2020 20:57:08 +0000

function validParenthesis(str) {

    let closingMap = {
        ')' : '(',
        ']' : '[',
        '}' : '{'
    }

    let chars = [];
    for(let i = 0; i < str.length; i++) {
        if (str[i] === '(' || str[i] === '[' || str[i] === '{') {
            chars.push(str[i]);
        }
        else {
            let compare = chars.pop();
            if (closingMap[str[i]] !== compare) return false;
        }
    }
    return chars.length === 0;
}

Binary Search

Ronald — Mon, 11 May 2020 20:52:28 +0000

function binarySearch(arr, n, start = 0, end = arr.length) {
    let mid = Math.floor((end + start) / 2);
    if (arr[mid] === n) return mid;

    if (start < end - 1) {
        if (n > arr[mid]) {
            return binarySearch(arr, n, mid, end);
        } else {
            return binarySearch(arr, n, start, mid);
        }
    }
    return -1;
}

Is Same Tree

Ron — Mon, 11 May 2020 20:45:14 +0000

let isSameTree = function(p, q) {

    if (p === q) return true;
    if (p?.val !== q?.val) return false;

    return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
};

Invert a Binary Tree

Ron — Mon, 11 May 2020 20:28:32 +0000

let invertTree = function(root) {

    if (root) {
        const right = root.right;
        root.right = invertTree(root.left)
        root.left = invertTree(right)
        return root;
    }
    return null;
};