median of arrays

medianofarrays/medianofarrays.go

@@ -0,0 +1,48 @@
+package medianofarrays
+
+import (
+	"math"
+)
+
+func median(xs []int) float64 {
+	half := float64(len(xs)) / 2
+	if len(xs)%2 == 0 {
+		return float64(xs[int(half)]+xs[int(half-1)]) / 2
+	}
+
+	return float64(xs[int(half)])
+}
+
+func sever(xs []int) (head int, tail []int) {
+	if len(xs) > 0 {
+		return xs[0], xs[1:]
+	}
+	return math.MaxInt, xs
+}
+
+func findMedianSortedArrays(nums1 []int, nums2 []int) float64 {
+	if len(nums1) == 0 && len(nums2) == 0 {
+		return math.NaN()
+	}
+	combined := make([]int, len(nums1)+len(nums2))
+
+	for i := range combined {
+		lhead, ltail := sever(nums1)
+		rhead, rtail := sever(nums2)
+
+		if lhead < rhead {
+			combined[i] = lhead
+			nums1 = ltail
+		} else {
+			combined[i] = rhead
+			nums2 = rtail
+		}
+	}
+
+	return median(combined)
+}
+
+func FindMedianSortedArrays(nums1 []int, nums2 []int) float64 {
+	return findMedianSortedArrays(nums1, nums2)
+
+}

medianofarrays/medianofarrays_test.go

@@ -0,0 +1,39 @@
+package medianofarrays_test
+
+import (
+	"math"
+	"testing"
+
+	"git.jxs.me/leetgo/medianofarrays"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEmpty(t *testing.T) {
+	actual := medianofarrays.FindMedianSortedArrays([]int{}, []int{})
+	require.InDelta(t, math.NaN(), actual, 0)
+}
+
+func TestRightEmpty(t *testing.T) {
+	actual := medianofarrays.FindMedianSortedArrays([]int{1, 2, 3}, []int{})
+	require.Equal(t, 2.0, actual)
+}
+
+func TestLeftEmpty(t *testing.T) {
+	actual := medianofarrays.FindMedianSortedArrays([]int{4, 5, 6}, []int{})
+	require.Equal(t, 5.0, actual)
+}
+
+func TestEven(t *testing.T) {
+	actual := medianofarrays.FindMedianSortedArrays([]int{1, 3, 5}, []int{7, 11, 13})
+	require.Equal(t, 6.0, actual)
+}
+
+func TestOverlap(t *testing.T) {
+	actual := medianofarrays.FindMedianSortedArrays([]int{1, 7, 23}, []int{1, 7, 11, 17})
+	require.Equal(t, 7.0, actual)
+}
+
+func TestExample1(t *testing.T) {
+	actual := medianofarrays.FindMedianSortedArrays([]int{1, 2}, []int{3, 4})
+	require.Equal(t, 2.5, actual)
+}

medianofarrays/readme.md

@@ -0,0 +1,32 @@
+4. Median of Two Sorted Arrays
+Hard
+
+Given two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays.
+
+The overall run time complexity should be O(log (m+n)).
+
+ 
+
+Example 1:
+
+Input: nums1 = [1,3], nums2 = [2]
+Output: 2.00000
+Explanation: merged array = [1,2,3] and median is 2.
+
+Example 2:
+
+Input: nums1 = [1,2], nums2 = [3,4]
+Output: 2.50000
+Explanation: merged array = [1,2,3,4] and median is (2 + 3) / 2 = 2.5.
+
+ 
+
+Constraints:
+
+    nums1.length == m
+    nums2.length == n
+    0 <= m <= 1000
+    0 <= n <= 1000
+    1 <= m + n <= 2000
+    -106 <= nums1[i], nums2[i] <= 106
+