To the next element, we need to add arrīoth the recursive solution takes O(n) time and O(n) extra memory, because there will be O(n) Activation records (stack frames) of recursive functions.

Add previous element's sum to first element void addPrevRec2(int *arr, int n, int sum=0) Initial value of sum should be 0 (because nothing need to be added to arr. Let us say, we are passing, sum of all previous elements to be added to the next element. In this case we need to pass one extra element (either the index, sum or some other value). We can also try to use tail recursion, where we first solve it to i’th index and then ask the recursion to solve it for rest of the array. we just need to add (n-1)th element to n'th elementĪbove approach is using head recursion. Since I got n matrices, I want to have a loop or similar, so I don't have to call every matrix by name like A1 + A2 + A3 + A4. Add all prev elements for first n-1 elements Now I want to sum them up, element by element so the result is one 100x100 matrix. if we are first element, don't do anything Once the problem is solved for first n-1 elements, we just need to add the value of (n-1)’th to the n’th element. Solve the problem for first n-1 elements (using recursion).

In the recursive solution we can either move forward (bottom-up) or backward (top-down). The above code takes O(n) time visiting each element only once. So we just need to add arr to arr as shown below: void addPrev(int* arr, int n) By the time we reach arr, arr already stores the sum of all elements from 0 to i-1. We are adding all the previous elements to each element in the array, but the solution does not require two loops. For example, if the input array is įirst, let us look at the non-recursive solution. Question: Given an array, arr of integers, write a recursive function that add sum of all the previous numbers to each index of the array. For example, if A is a matrix, then sum (A, 1 2) is the sum of all elements in A, since every element of a matrix is contained in the array slice defined by dimensions 1 and 2. This question is from exercise in my book Dynamic Programming for Coding Interviews (Question: 1.2, Page-5) S sum (A,vecdim) sums the elements of A based on the dimensions specified in the vector vecdim.

Matlab 2017 sum every element matrix