[playground] binary search

playground/p4/p4.go

@@ -0,0 +1,53 @@
+// Copyright 2020, Chef.  All rights reserved.
+// https://github.com/q191201771/naza
+//
+// Use of this source code is governed by a MIT-style license
+// that can be found in the License file.
+//
+// Author: Chef (191201771@qq.com)
+
+package main
+
+import (
+	"fmt"
+	//"sort"
+)
+
+// 把 sort.Search 拷过来，加些单步日志
+func SearchWithLog(n int, f func(int) bool) int {
+	i, j := 0, n
+	for i < j {
+		h := int(uint(i+j) >> 1)
+		fmt.Printf("i=%d, j=%d, h=%d", i, j, h)
+		if !f(h) {
+			fmt.Println(" not match.")
+			i = h + 1
+		} else {
+			fmt.Println("match.")
+			j = h
+		}
+	}
+	return i
+}
+
+func main() {
+	const key = 3
+	arr := []int{1, 3, 5, 7}
+	index := SearchWithLog(len(arr), func(i int) bool {
+		//return arr[i] == 3
+		//return arr[i] >= 3
+		return arr[i] >= key
+		//return arr[i] >= 9
+		//return arr[i] >= 2
+	})
+	fmt.Printf("index=%d\n", index)
+	if index < len(arr) && arr[index] == key {
+		fmt.Println("exist")
+	} else {
+		fmt.Println("not exist")
+	}
+
+	//var tmp uint
+	//tmp = uint(2147483647 + 2147483647)
+	//fmt.Println(tmp)
+}