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
#include <vector>
class Solution {
public:
std::vector<int> productExceptSelf(std::vector<int>& nums) {
int product = 1;
std::vector<int> ans(nums.size(), 1);
for (int num : nums) {
product *= num;
}
for (int i = 0; i < nums.size(); i++) {
if (nums[i] != 0) {
ans[i] = product / nums[i];
} else {
int p = 1;
for (int j = 0; j < nums.size(); j++) {
if (j != i) {
p *= nums[j];
}
}
ans[i] = p;
}
}
return ans;
}
};