✅238. 除自身以外数组的乘积 about like-algorithms HOT 2 OPEN

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var productExceptSelf = function (nums) {
    let result = new Array(nums.length).fill(1);

    let product = 1; // 保证统一性

    for (let i = 0; i < nums.length; i++) {
        result[i] = result[i] * product;
        product = nums[i] * product;
    }

    product = 1;

    for (let i = nums.length - 1; i >= 0; i--) {
        result[i] = result[i] * product;
        product = nums[i] * product;
    }

    return result;
};

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var productExceptSelf = function(nums) {
    const len = nums.length;
	const dp1 = Array(len).fill(0);
	dp1[0] = 1;

	for (let i = 1; i < len; i++) {
		dp1[i] = dp1[i - 1] * nums[i - 1];
	}
	
	const dp2 = Array(len).fill(0);
	dp2[len - 1] = 1;
	for (let i = len - 2; i >= 0; i--) {
		dp2[i] = dp2[i + 1] * nums[i + 1];
	}
	
	const ret = [];
	for (let i = 0; i < len; i++) {
		ret[i] = dp1[i] * dp2[i];
	}
	return ret;
};