Range Sum Query 2D - Immutable | Prefix Sum on Matrix | Dp | 304 LeetCode | Day 12

Here is the detailed solution of LEETCODE DAY 12 RANGE SUM QUERY 2D IMMUTABLE Problem of May Leetcoding Challenge and if you have any doubts , do comment below to let us know and help you.

In this Video, I have discussed the best solution for the problem. I have
explained how to compute the prefix sum on matrix and answer for every query in O(1) with some prerequisite calculation.

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Timestamps:-
Introduction:- 00:00
Problem Statement:- 00:14
Explanation With Example:- 02:10
Explanation in detail:- 07:47
Code:- 12:50

Link to Code:-

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[er-wlsy]

Since we are given the start and endpoint of the rectangle and we know the size of the matrix can't we iterate the rows and cols until the endpoint and sum the elements? For example, the start (1, 1) and end (2, 3) size of the matrix is 4 x 5. Then indices are row = 1, 2 and cols = 1, 2, 3 so we will have (1, 1) (1, 2) (1, 3) and (2, 1) (2, 2) (2, 3) since we hit the end return the sum of indices. Can't this be done in constant time