add solution 0004 [golang]

Author: lightfish-zhang

solution/0004.Median of Two Sorted Arrays/Solution.go

@@ -0,0 +1,68 @@
+/*
+ * Report by leetcode.com
+ * Runtime: 16 ms, Memory Usage: 5.4 MB
+ */
+func findMedianSortedArrays(nums1 []int, nums2 []int) float64 {
+	mathMax := func(a, b int) int {
+		if a > b {
+			return a
+		}
+		return b
+	}
+	mathMin := func(a, b int) int {
+		if a < b {
+			return a
+		}
+		return b
+	}
+
+	var len1, len2 int
+	len1 = len(nums1)
+	len2 = len(nums2)
+	if len1 > len2 {
+		var tmp []int = nums1
+		nums1 = nums2
+		nums2 = tmp
+		var t int = len1
+		len1 = len2
+		len2 = t
+	}
+
+	var min, max int = 0, 0
+	max = len1
+
+	halfLen := (len1 + len2 + 1) / 2
+
+	for min <= max {
+		i := (min + max) / 2
+		j := halfLen - i
+
+		if i < max && nums2[j-1] > nums1[i] {
+			min++
+		} else if i > min && nums1[i-1] > nums2[j] {
+			max--
+		} else {
+			var maxLeft int
+			if i == 0 {
+				maxLeft = nums2[j-1]
+			} else if j == 0 {
+				maxLeft = nums1[i-1]
+			} else {
+				maxLeft = mathMax(nums1[i-1], nums2[j-1])
+			}
+			if ((len1 + len2) & 1) == 1 {
+				return float64(maxLeft)
+			}
+			var minRight int
+			if i == len1 {
+				minRight = nums2[j]
+			} else if j == len2 {
+				minRight = nums1[i]
+			} else {
+				minRight = mathMin(nums2[j], nums1[i])
+			}
+			return float64(maxLeft+minRight) / 2
+		}
+	}
+	return 0
+}