1299. Replace Elements with Greatest Element on Right Side (easy)

Q:

Given an array arr, replace every element in that array with the greatest element among the elements to its right, and replace the last element with -1.

After doing so, return the array.

Example 1:

Input: arr = [17,18,5,4,6,1]
Output: [18,6,6,6,1,-1]

Constraints:

• 1 <= arr.length <= 10^4
• 1 <= arr[i] <= 10^5

A:

class Solution {
public:
    vector<int> replaceElements(vector<int>& arr) {
        // search from right and record the so far greatet
        // declaring new vector and copying element of old vector, constructgor method, deep copy
        vector<int> res(arr); 
        int n = arr.size();
        int sofar = -1, tmp=0;
        for(int j = n-1;j>=0; --j)
        {
            tmp = max(sofar, res[j]);
            res[j] = sofar;
            sofar = tmp;
        }
        return res;
    }
};