LeetCode-in-All
238. Product of Array Except Self
Medium
Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i].
The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.
You must write an algorithm that runs in O(n) time and without using the division operation.
Example 1:
Input: nums = [1,2,3,4]
Output: [24,12,8,6]
Example 2:
Input: nums = [-1,1,0,-3,3]
Output: [0,0,9,0,0]
Constraints:
2 <= nums.length <= 105-30 <= nums[i] <= 30- The product of any prefix or suffix of
numsis guaranteed to fit in a 32-bit integer.
Follow up: Can you solve the problem in O(1) extra space complexity? (The output array does not count as extra space for space complexity analysis.)
Solution
class Solution {
List<int> productExceptSelf(List<int> nums) {
int product = 1;
List<int> ans = List.filled(nums.length, 0);
// Calculate total product of all elements
for (int num in nums) {
product *= num;
}
// Fill in the result array
for (int i = 0; i < nums.length; i++) {
if (nums[i] != 0) {
ans[i] = product ~/ nums[i]; // Integer division
} else {
int p = 1;
for (int j = 0; j < nums.length; j++) {
if (j != i) {
p *= nums[j];
}
}
ans[i] = p;
}
}
return ans;
}
}