Problem
Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].
Solve it without division and in O(n).
ExampleFor example, given [1,2,3,4], return [24,12,8,6].
Follow up:Could you solve it with constant space complexity? (Note: The output array does not count as extra space for the purpose of space complexity analysis.)
Solutionclass Solution { public int[] productExceptSelf(int[] nums) { long product = 1; int[] res = new int[nums.length]; for (int i = 0; i < nums.length; i++) { //so there are two special situations: one number or more than one number equals 0 if (nums[i] != 0) product *= (long) nums[i]; else { //here we consider if one number is 0 //all other products should be 0 Arrays.fill(res, 0); //*maybe* except for this one, lets create a method for it res[i] = getProduct(nums, i); //stop here and return, since we already got the correct result array //*and* no need to consider the other situation, it would be all 0"s return res; } } for (int i = 0; i < res.length; i++) { res[i] = (int) (product / nums[i]); } return res; } public int getProduct(int[] nums, int k) { int product = 1; for (int i = 0; i < nums.length; i++) { if (i != k) product *= nums[i]; } return product; } }Update 2018-9
//Solution without division class Solution { public int[] productExceptSelf(int[] nums) { int n = nums.length; int[] res = new int[n]; int[] dp = new int[n]; int[] pd = new int[n]; dp[0] = nums[0]; for (int i = 1; i < n; i++) { dp[i] = dp[i-1] * nums[i]; } pd[n-1] = nums[n-1]; for (int i = n-2; i > 0; i--) { pd[i] = pd[i+1] * nums[i]; } res[0] = pd[1]; res[n-1] = dp[n-2]; for (int i = 1; i < n-1; i++) { res[i] = dp[i-1] * pd[i+1]; } return res; } }
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Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].Solve it without division and in O(n). For...
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Problem Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i]. Solve it without division and in ...
問題:Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i]. Solve it without division and in O(n)....
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