# GeetCode Hub

Given a 2D matrix `matrix`, handle multiple queries of the following type:

1. Calculate the sum of the elements of `matrix` inside the rectangle defined by its upper left corner `(row1, col1)` and lower right corner `(row2, col2)`.

Implement the NumMatrix class:

• `NumMatrix(int[][] matrix)` Initializes the object with the integer matrix `matrix`.
• `int sumRegion(int row1, int col1, int row2, int col2)` Returns the sum of the elements of `matrix` inside the rectangle defined by its upper left corner `(row1, col1)` and lower right corner `(row2, col2)`.

Example 1:

```Input
["NumMatrix", "sumRegion", "sumRegion", "sumRegion"]
[[[[3, 0, 1, 4, 2], [5, 6, 3, 2, 1], [1, 2, 0, 1, 5], [4, 1, 0, 1, 7], [1, 0, 3, 0, 5]]], [2, 1, 4, 3], [1, 1, 2, 2], [1, 2, 2, 4]]
Output
[null, 8, 11, 12]

Explanation
NumMatrix numMatrix = new NumMatrix([[3, 0, 1, 4, 2], [5, 6, 3, 2, 1], [1, 2, 0, 1, 5], [4, 1, 0, 1, 7], [1, 0, 3, 0, 5]]);
numMatrix.sumRegion(2, 1, 4, 3); // return 8 (i.e sum of the red rectangle)
numMatrix.sumRegion(1, 1, 2, 2); // return 11 (i.e sum of the green rectangle)
numMatrix.sumRegion(1, 2, 2, 4); // return 12 (i.e sum of the blue rectangle)
```

Constraints:

• `m == matrix.length`
• `n == matrix[i].length`
• `1 <= m, n <= 200`
• `-105 <= matrix[i][j] <= 105`
• `0 <= row1 <= row2 < m`
• `0 <= col1 <= col2 < n`
• At most `104` calls will be made to `sumRegion`.

class NumMatrix { public NumMatrix(int[][] matrix) { } public int sumRegion(int row1, int col1, int row2, int col2) { } } /** * Your NumMatrix object will be instantiated and called as such: * NumMatrix obj = new NumMatrix(matrix); * int param_1 = obj.sumRegion(row1,col1,row2,col2); */