Delete one or except itself

238. Product of Array Except Self

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

1186. Maximum Subarray Sum with One Deletion

reference:https://leetcode.com/problems/maximum-subarray-sum-with-one-deletion/discuss/377522/C++-forward-and-backward-soluti

class Solution {
public:
    int maximumSum(vector<int>& arr) {
        const int n=arr.size();
        if(n==1)return arr[0];
        vector<int> left(n), right(n);
        left[0]=arr[0], right[n-1]=arr[n-1];
        for (int i=1;i<n;++i){
            left[i] = max(left[i-1],0)+arr[i];
        }
        for (int i=n-2;i>=0;--i){
            right[i] =max(0,right[i+1])+arr[i];
        }
        int res = -(1<<30);
        for (int i=0;i<n;++i){
            if(i==0)res=max(res, right[i+1]);
            else if(i==n-1)res=max(res,left[i-1]);
            else {
                res = max(res, right[i+1]);
                res = max(res, left[i-1]);
                res = max(res, left[i-1]+right[i+1]);     
            }
        
        }
        return res;
    }
};