From 1d211d12e17eaff59351d838053989ee125dbb0d Mon Sep 17 00:00:00 2001
From: Yu Zhao <yu.zhao@joudou.com>
Date: Sat, 12 May 2018 12:31:45 +0800
Subject: [PATCH] update

---
 ch04/4.5_set.go  | 27 ++++++++++++++++++++++++
 ch05/ex1.go      | 29 ++++++++++++++++++++++++++
 ch05/ex2.go      | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
 ch05/search2d.go | 37 +++++++++++++++++++++++++++++++++
 4 files changed, 147 insertions(+)
 create mode 100644 ch04/4.5_set.go
 create mode 100644 ch05/ex1.go
 create mode 100644 ch05/ex2.go
 create mode 100644 ch05/search2d.go

diff --git a/ch04/4.5_set.go b/ch04/4.5_set.go
new file mode 100644
index 0000000..9ac23e4
--- /dev/null
+++ b/ch04/4.5_set.go
@@ -0,0 +1,27 @@
+package main
+
+import "fmt"
+
+type Set map[interface{}]bool
+
+func (s *Set) Add(key interface{}) {
+	(*s)[key] = true
+}
+
+func (s *Set) Remove(key interface{}) {
+	delete((*s), key)
+}
+
+func (s *Set) Find(key interface{}) bool {
+	return (*s)[key]
+}
+
+func main() {
+	mp := make(Set)
+	mp.Add("a")
+	mp.Add("b")
+	mp.Add("a")
+	fmt.Println(mp.Find("a"))
+	fmt.Println(mp.Find("b"))
+	fmt.Println(mp.Find("c"))
+}
diff --git a/ch05/ex1.go b/ch05/ex1.go
new file mode 100644
index 0000000..d2eaa64
--- /dev/null
+++ b/ch05/ex1.go
@@ -0,0 +1,29 @@
+// find first repeated in a list
+
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	arr1 := []int{1,2,3,1,2,3}
+	arr2 := []int{1,1,0,0}
+	arr3 := []int{1,2,3,4,5}
+	fmt.Println(findFirstRepeat(arr1))
+	fmt.Println(findFirstRepeat(arr2))
+	fmt.Println(findFirstRepeat(arr3))
+}
+
+
+func findFirstRepeat(arr []int) (int, bool) { // return index, found
+	table := make(map[int]bool, len(arr))
+	for index, item := range arr {
+		if !table[item] {
+			table[item] = true
+		} else {
+			return index, true
+		}
+	}
+	return -1, false
+}
diff --git a/ch05/ex2.go b/ch05/ex2.go
new file mode 100644
index 0000000..3682ecb
--- /dev/null
+++ b/ch05/ex2.go
@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+)
+
+func main() {
+	arr := []int{1,5,6,7,2,8,3,4,9}
+
+	fmt.Println(find3ForSum(arr, 13))
+	fmt.Println(find3ForSum1(arr, 13))
+}
+
+func find3ForSum(arr []int, sum int) (int, int, int, bool) {
+	// brute force, O(n^3)
+	length := len(arr)
+
+	for i := 0; i < length - 2; i ++ {
+		for j := i + 1; j < length - 1; j ++ {
+			for k := j + 1; k < length; k ++ {
+				if arr[i] + arr[j] + arr[k] == sum {
+					return arr[i], arr[j], arr[k], true
+				}
+			}
+		}
+	}
+	return -1, -1, -1, false
+}
+
+func find3ForSum1(arr []int, sum int) (int, int, int, bool) {
+	sort.Slice(arr, func (i, j int) bool {
+		return arr[i] < arr[j]
+	})
+	// fmt.Println(arr)
+
+	length := len(arr)
+
+	for i := 0; i < length - 2; i ++ {
+		j := i + 1
+		k := length - 1
+		for ; j < length - 1 && k > j; {
+			temp := arr[i] + arr[j] + arr[k]
+			if temp == sum {
+				return arr[i], arr[j], arr[k], true
+			} else if temp > sum {
+				k --
+			} else {
+				j ++
+			}
+		}
+	}
+	return -1, -1, -1, false
+}
diff --git a/ch05/search2d.go b/ch05/search2d.go
new file mode 100644
index 0000000..bb5fcb7
--- /dev/null
+++ b/ch05/search2d.go
@@ -0,0 +1,37 @@
+// 5.37
+package main
+
+import "fmt"
+
+func main() {
+	matrix := [][]int{
+		[]int{1,11,21,31},
+		[]int{2,12,22,32},
+		[]int{3,13,23,33},
+		[]int{4,14,24,34}}
+
+	fmt.Println(find2d(matrix, -1))
+	fmt.Println(find2d(matrix, 1))
+	fmt.Println(find2d(matrix, 31))
+	fmt.Println(find2d(matrix, 2))
+	fmt.Println(find2d(matrix, 13))
+	fmt.Println(find2d(matrix, 4))
+	fmt.Println(find2d(matrix, 34))
+	fmt.Println(find2d(matrix, 100))
+}
+
+func find2d(matrix[][]int, target int) (row, col int) {
+	col = len(matrix[0]) - 1
+
+	for row < len(matrix) && col >= 0 {
+		this := matrix[row][col]
+		if this == target {
+			return
+		} else if this < target {
+			row ++
+		} else {
+			col --
+		}
+	}
+	return -1, -1
+}