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top-100-liked/65/leetcode_test.go

@@ -0,0 +1,58 @@
+package top100liked
+
+import (
+	"fmt"
+	"testing"
+)
+
+// https://leetcode.cn/problems/find-first-and-last-position-of-element-in-sorted-array/?envType=study-plan-v2&envId=top-100-liked
+
+func binarySearch(nums []int, target int) int {
+	start := 0
+	end := len(nums) - 1
+	for start <= end {
+		midIdx := start + (end-start)/2
+		mid := nums[midIdx]
+		if mid == target {
+			return midIdx
+		} else if mid > target {
+			end = midIdx - 1
+		} else if mid < target {
+			start = midIdx + 1
+		}
+	}
+	return -1
+}
+
+func searchRange(nums []int, target int) []int {
+	res := binarySearch(nums, target)
+	if res == -1 {
+		return []int{-1, -1}
+	}
+
+	l, r := res-1, res+1
+	for l >= 0 {
+		_l := binarySearch(nums[:l+1], target)
+		if _l == -1 {
+			break
+		} else {
+			l = _l - 1
+		}
+	}
+	for r < len(nums) {
+		_r := binarySearch(nums[r:], target)
+		if _r == -1 {
+			break
+		} else {
+			r = r + _r + 1
+		}
+	}
+	return []int{l + 1, r - 1}
+}
+
+func Test(t *testing.T) {
+	nums := []int{5, 7, 7, 8, 8, 10}
+	fmt.Printf("%+v\n", searchRange(nums, 8))
+	fmt.Printf("%+v\n", searchRange(nums, 6))
+	fmt.Printf("%+v\n", searchRange([]int{}, 0))
+}