add new solutions

solutions/8/q852/solution.go

@@ -0,0 +1,17 @@
+// Package q852 implements a solution for https://leetcode.com/problems/peak-index-in-a-mountain-array/
+package q852
+
+func peakIndexInMountainArray(arr []int) int {
+	l, r := 0, len(arr)-1
+	for l < r {
+		m := (l + r) / 2
+		if arr[m] < arr[m+1] { // incrementing
+			l = m + 1
+		} else {
+			r = m
+		}
+	}
+	return l
+}
+
+var _ = peakIndexInMountainArray