answer a few more questions

2 files changed, 93 insertions, 1 deletions

diff --git a/0x01/README.md b/0x01/README.md
index 38bed54..ec5a526 100644
--- a/0x01/README.md
+++ b/0x01/README.md
@@ -310,7 +310,27 @@ properties.
 
 1. Exercise 4.1-2 from the textbook (10 marks)
 
-  What does `FIND-MAXIMUM-SUBARRAY` return when all elements of `A` are negative?
+  Write pseudocode for the brute-force method of solving the maximum-subarray
+  problem. Your procedure should run in `theta(n^2)` time.
+
+  The following brute force solution uses a nested loop that yields a worst case
+  of `n^2` iterations.
+
+  ```
+  FIND-MAXIMUM-SUBARRAY(A,low,high)
+    l = low
+    r = high
+    total = -1
+    for i = low to high
+      sum = 0
+      for j = i to high
+        sum = sum + A[j]
+        if sum > total
+          total = sum
+          l = i
+          r = j
+    return l, r, total
+  ```
 
 1. Exercise 4.2-1 from the textbook (5 marks)
 
@@ -323,6 +343,35 @@ properties.
 
   Show your work.
 
+  ```plaintext
+  Strassens algorithm:
+
+          n
+  cij = sigma ai*k * bkj
+         k=1
+
+  c11 = a11 * b11 + a12 * b21
+  c12 = a11 * b12 + a12 * b22
+  c21 = a21 * b11 + a22 * b21
+  c22 = a21 * b12 + a22 * b22
+
+  A = |a11 a12| B = |b11 b12|
+      |a21 a22|     |b21 b22|
+  A = |1 3|     B = |6 8|
+      |7 5|         |4 2|
+
+  c11 = (1 * 6) + (3 * 4) = 18
+  c12 = (1 * 8) + (3 * 2) = 14
+  c21 = (7 * 6) + (5 * 4) = 62
+  c22 = (7 * 8) + (5 * 2) = 66
+
+  |c11 c12|
+  |c21 c22|
+
+  |18 14|
+  |62 66|
+  ```
+
 1. Exercise 4.3-2 from the textbook (10 marks)
 
   Show that the solution of `T(n) = T([n/2]) + 1` is `O(lg n)`
diff --git a/exercises/4.1-2/max_subarray_test.go b/exercises/4.1-2/max_subarray_test.go
new file mode 100644
index 0000000..920a3fb
--- /dev/null
+++ b/exercises/4.1-2/max_subarray_test.go
@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+)
+
+func MaxSubArray(a []int, low int, high int) (int, int, int) {
+	left := low
+	right := high
+	sum := -1
+
+	for i := low; i < high; i++ {
+		tempSum := 0
+		for j := i; j < high; j++ {
+			tempSum = tempSum + a[j]
+			if tempSum > sum {
+				sum = tempSum
+				left = i
+				right = j
+			}
+		}
+	}
+	return left, right, sum
+}
+
+func TestMergeSort(t *testing.T) {
+	t.Run("", func(t *testing.T) {
+		items := []int{100, 113, 110, 85, 105, 102, 86, 63, 81, 101, 94, 106, 101, 79, 94, 90, 97}
+		l, r, total := MaxSubArray(items, 0, len(items))
+
+		fmt.Println(l, r, total)
+		if l != 0 {
+			t.Errorf("Expected: %v, Got: %v", 0, l)
+		}
+		if r != 16 {
+			t.Errorf("Expected: %v, Got: %v", 16, r)
+		}
+		if total != 1607 {
+			t.Errorf("Expected: %v, Got: %v", 1607, total)
+		}
+	})
+}