238 除自身以外数组的乘积

https://leetcode.cn/leetbook/read/top-interview-questions-hard/xw8dz6/

cost:

class Solution {
public:
    vector<int> productExceptSelf(vector<int>& nums) {
        vector<int> res(nums.size(), 0);
        res[0] = 1;
        for (int i = 1; i < nums.size(); i++) {
            res[i] = nums[i - 1] * res[i - 1];
        }
        int lastNum = nums[nums.size() - 1];
        nums[nums.size() - 1] = 1;
        for (int i = nums.size() - 2; i >= 0; i--) {
            int product = nums[i + 1] * lastNum;
            lastNum = nums[i];
            nums[i] = product;
        }
        for (int i = 0; i < nums.size(); i++) {
            res[i] = res[i] * nums[i];
        }
        return res;
    }
};