Create question3_2.go

go/chapter03/question3_2.go

@@ -0,0 +1,105 @@
+// Author: Sini Tinfors (sinitin) <sini.tinfors@gmail.com>
+
+/*
+How would you design a stack which,
+in addition to push and pop, also has a
+function min which returns the minimum element?
+Push, pop and min should all operate in O(1) time.
+*/
+
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+var stackpointer = []int{-1, -1, -1}
+
+type nodewithmin struct {
+	value int
+	min   int
+}
+
+func main() {
+	var triplearr [30]nodewithmin
+	rand.Seed(time.Now().UTC().UnixNano())
+
+	//populate the three stacks
+	for i := 0; i < 3; i++ {
+		for j := 0; j < 10; j++ {
+			val := random(0, 100)
+			push(&triplearr, i, val)
+		}
+	}
+
+	//print the three stacks
+	for i := 0; i < 3; i++ {
+		for j := 0; j < 10; j++ {
+			fmt.Println(triplearr[j+(10*i)])
+		}
+		fmt.Println("")
+	}
+
+	a := min(&triplearr, 0)
+	fmt.Println("The min value of stack 0 is: ")
+	fmt.Printf("%v\n", a)
+
+	b := min(&triplearr, 1)
+	fmt.Println("The min value of stack 1 is: ")
+	fmt.Printf("%v\n", b)
+
+	c := min(&triplearr, 2)
+	fmt.Println("The min value of stack 2 is: ")
+	fmt.Printf("%v\n", c)
+}
+
+func peek(s *[30]nodewithmin, stack int) (int, int) {
+	if stackpointer[stack] == -1 {
+		return -1, -1
+	}
+
+	return s[stackpointer[stack]+(stack*10)].min, s[stackpointer[stack]+(stack*10)].value
+}
+
+func push(s *[30]nodewithmin, stack, value int) {
+	//check if empty
+	if stackpointer[stack] == -1 {
+		s[(stack * 10)].value = value
+		s[(stack * 10)].min = value
+		stackpointer[stack] = 0
+	} else {
+
+		s[stackpointer[stack]+(stack*10)+1].value = value
+		i, _ := peek(s, stack)
+
+		if i < value {
+
+			s[(stack*10)+stackpointer[stack]+1].min = i
+		} else {
+			s[(stack*10)+stackpointer[stack]+1].min = value
+		}
+
+		stackpointer[stack] = stackpointer[stack] + 1
+	}
+}
+
+func pop(s *[30]nodewithmin, stack int) nodewithmin {
+	returnvalue := s[stackpointer[stack]]
+	stackpointer[stack] = stackpointer[stack] - 1
+	return returnvalue
+}
+
+func min(s *[30]nodewithmin, stack int) int {
+	//check if empty
+	if stackpointer[stack] == -1 {
+		return -1
+	} else {
+		return s[stackpointer[stack]+(stack*10)].min
+	}
+}
+
+func random(min int, max int) int {
+	return min + rand.Intn(max-min)
+}