add 在排序数组中查找数字 I

leetcode/剑指offer/在排序数组中查找数字 I/main.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	input := bufio.NewScanner(os.Stdin)
+	var output int
+	var digits []int
+	var target int
+	for input.Scan() {
+		line := input.Text()
+
+		digits = []int{}
+		values := strings.Split(line, " ")
+		length := len(values)
+
+		for index, v := range values {
+			d, _ := strconv.Atoi(v)
+			if index == length-1 {
+				target = d
+				break
+			}
+			digits = append(digits, d)
+		}
+
+		output = search(digits, target)
+		fmt.Println(output)
+	}
+}
+func search(nums []int, target int) int {
+	var count int
+	for _, v := range nums {
+		if v == target {
+			count++
+		}
+	}
+
+	return count
+}

leetcode/剑指offer/在排序数组中查找数字 I/main_optimize.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	input := bufio.NewScanner(os.Stdin)
+	var output int
+	var digits []int
+	var target int
+	for input.Scan() {
+		line := input.Text()
+
+		digits = []int{}
+		values := strings.Split(line, " ")
+		length := len(values)
+
+		for index, v := range values {
+			d, _ := strconv.Atoi(v)
+			if index == length-1 {
+				target = d
+				break
+			}
+			digits = append(digits, d)
+		}
+
+		fmt.Println("start ---", digits, target)
+		output = search(digits, target)
+		fmt.Println(output)
+	}
+}
+func search(nums []int, target int) int {
+	if len(nums) == 0 {
+		return 0
+	}
+	var leftIdx = binarySearchLeft(nums, target)
+	var rightIdx = binarySearchLeft(nums, target+1)
+
+	if nums[leftIdx] != target {
+		return 0
+	}
+	if leftIdx == rightIdx {
+		return 1
+	}
+	if nums[rightIdx] == target {
+		rightIdx += 1
+	}
+	return rightIdx - leftIdx
+}
+
+// left最后都会和right相等，nums[right]永远大于等于target。
+// 就会使得nums[left]永远小于等于target.for结束的时候left和right相等，
+// 所以只需要判断nums[left] ?= target, 就能判断nums中是否存在target
+func binarySearchLeft(nums []int, target int) int {
+	var left, right = 0, len(nums) - 1
+	var mid int
+	for left < right {
+		mid = (left + right) / 2
+		if nums[mid] >= target {
+			right = mid
+		} else {
+			left = mid + 1
+		}
+	}
+
+	return left
+}