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
impl Solution {
pub fn product_except_self(nums: Vec<i32>) -> Vec<i32> {
let mut res = Vec::new();
let mut prev = nums[0];
let n = nums.len();
// calc prefix
res.push(1);
for i in 1..n{
let mut prod = 1;
prod *= prev;
prev *= nums[i];
res.push(prod);
}
// calc suffix
prev = nums[n - 1];
for i in (0..n - 1).rev(){
let mut prod = 1;
prod *= prev;
prev *= nums[i];
res[i] *= prod;
}
res
}
}