Add maximum subarray and range sum query 2d immutable

Author: Gituser143

Easy/README.md

@@ -23,6 +23,7 @@ Easy
 - [maximum-ascending-subarray-sum.md](Easy/maximum-ascending-subarray-sum.md)
 - [maximum-depth-of-binary-tree.md](Easy/maximum-depth-of-binary-tree.md)
 - [maximum-depth-of-n-ary-tree.md](Easy/maximum-depth-of-n-ary-tree.md)
+- [maximum-subarray.md](Easy/maximum-subarray.md)
 - [merge-sorted-array.md](Easy/merge-sorted-array.md)
 - [merge-two-sorted-lists.md](Easy/merge-two-sorted-lists.md)
 - [minimum-depth-of-binary-tree.md](Easy/minimum-depth-of-binary-tree.md)

Easy/maximum-subarray.md

@@ -0,0 +1,27 @@
+Code
+====
+
+```go
+func maxSubArray(nums []int) int {
+	max := nums[0]
+	for i := 1; i < len(nums); i++ {
+		if nums[i]+nums[i-1] > nums[i] {
+			nums[i] = nums[i] + nums[i-1]
+		}
+		if nums[i] > max {
+			max = nums[i]
+		}
+	}
+
+	return max
+}
+```
+
+Solution in mind
+================
+
+-	We iterate through the array and replace the number at a given position by the maximum sum that can be created till that position.
+
+-	The number at a given position is thus set to the `max(nums[i], nums[i]+nums[i-1])`.
+
+-	Thus if a sum is lesser than the number itself, we're better off by using just the number.

Medium/README.md

@@ -51,6 +51,7 @@ Medium
 - [populating-next-right-pointers-in-each-node-ii.md](Medium/populating-next-right-pointers-in-each-node-ii.md)
 - [populating-next-right-pointers-in-each-node.md](Medium/populating-next-right-pointers-in-each-node.md)
 - [pseudo-palindromic-paths-in-a-binary-tree.md](Medium/pseudo-palindromic-paths-in-a-binary-tree.md)
+- [range-sum-query-2d-immutable.md](Medium/range-sum-query-2d-immutable.md)
 - [redundant-connection.md](Medium/redundant-connection.md)
 - [remove-comments.md](Medium/remove-comments.md)
 - [remove-duplicates-from-sorted-array-ii.md](Medium/remove-duplicates-from-sorted-array-ii.md)

Medium/range-sum-query-2d-immutable.md

@@ -0,0 +1,30 @@
+Code
+====
+
+```go
+type NumMatrix struct {
+	Matrix [][]int
+}
+
+func Constructor(matrix [][]int) NumMatrix {
+	n := NumMatrix{Matrix: matrix}
+	return n
+}
+
+func (this *NumMatrix) SumRegion(row1 int, col1 int, row2 int, col2 int) int {
+	sum := 0
+	for i := row1; i <= row2; i++ {
+		for j := col1; j <= col2; j++ {
+			sum += this.Matrix[i][j]
+		}
+	}
+
+	return sum
+}
+
+/**
+ * Your NumMatrix object will be instantiated and called as such:
+ * obj := Constructor(matrix);
+ * param_1 := obj.SumRegion(row1,col1,row2,col2);
+ */
+```

README.md

@@ -7,7 +7,7 @@ Link to profile, [bhargavsnv100](https://leetcode.com/bhargavsnv100/)
 
 | [Easy](Easy/README.md) | [Medium](Medium/README.md) | [Hard](Hard/README.md) |
 |------------------------|----------------------------|------------------------|
-| 47                     | 76                         | 14                     |
+| 48                     | 77                         | 14                     |
 
 Problems finished
 =================
@@ -37,6 +37,7 @@ Easy
 - [maximum-ascending-subarray-sum.md](Easy/maximum-ascending-subarray-sum.md)
 - [maximum-depth-of-binary-tree.md](Easy/maximum-depth-of-binary-tree.md)
 - [maximum-depth-of-n-ary-tree.md](Easy/maximum-depth-of-n-ary-tree.md)
+- [maximum-subarray.md](Easy/maximum-subarray.md)
 - [merge-sorted-array.md](Easy/merge-sorted-array.md)
 - [merge-two-sorted-lists.md](Easy/merge-two-sorted-lists.md)
 - [minimum-depth-of-binary-tree.md](Easy/minimum-depth-of-binary-tree.md)
@@ -116,6 +117,7 @@ Medium
 - [populating-next-right-pointers-in-each-node-ii.md](Medium/populating-next-right-pointers-in-each-node-ii.md)
 - [populating-next-right-pointers-in-each-node.md](Medium/populating-next-right-pointers-in-each-node.md)
 - [pseudo-palindromic-paths-in-a-binary-tree.md](Medium/pseudo-palindromic-paths-in-a-binary-tree.md)
+- [range-sum-query-2d-immutable.md](Medium/range-sum-query-2d-immutable.md)
 - [redundant-connection.md](Medium/redundant-connection.md)
 - [remove-comments.md](Medium/remove-comments.md)
 - [remove-duplicates-from-sorted-array-ii.md](Medium/remove-duplicates-from-sorted-array-ii.md)