Golang Tutorials

a_Golang.md

Go

Go, also known as Golang, is a statically typed, compiled programming language designed at Google by Robert Griesemer, Rob Pike, and Ken Thompson. Go is syntactically similar to C, but with memory safety, garbage collection, structural typing, and CSP-style concurrency.

b_Hello_World.go

package main

import "fmt"

func main() {
    fmt.Printf("hello, world\n")
}

c_workspace.md

Workspace for good Project Management in Golang

A Go workspace directory must have three sub-directories viz.

• src
• pkg
• bin

credits : https://medium.com/rungo/working-in-go-workspace-3b0576e0534a https://golang.org/doc/code.html#Organization

src

The src directory contains Go packages. A package in nutshell is a project directory containing Go source code (.go files). Any packages installed using go get command will reside here as well (and its dependency packages). In Go, every program is contained in a package. Hence, whenever you will be working with a new Go project, you need to create a new directory inside $GOPATH/src and work your way up from there.

pkg

The pkg directory contains Go package objects. They are the compiled versions of the original package source code and they have .a file extension (a stands for archived). These files contain the compiled package binary code, along with debugging symbols and source information. A package object is customized for machine architecture and the Go version. These files are created by the Go pack tool while building/installing a package.

bin

The bin directory contains the same binary executable files. These files are created by go install commands. go install command runs go build command internally and then outputs these files to the bin directory.

d_fmt.md

Println, Printf and Print

• The Print() function simply prints a list of variables to STDOUT with default formatting.
• The Printf() function allows you to specify the formatting using a format template.
• The Println() function works like Print() except it inserts spaces between the variables and appends a new line at the end.

Format Verbs

• %v the value in a default format
• %T a Go-syntax representation of the type of the value
• %d prints an integer in base-10
• %x and %X print an integer in base-16
• %f prints a floating point number without an exponent.
• %t the word true or false
• %o base 8
• %b base 2
• %q a double-quoted string safely escaped with Go syntax
• %p prints a pointer address of your variable.

Scanf, Scanln and Scan

• The Scan() function reads in space-delimited values into variables
• The Scanf() does the same but lets you specify formatting options using a format string.
• The Scanln() function works Scan() except that it does not treat newlines as spaces.

Credits : https://golang.org/pkg/fmt/ https://medium.com/go-walkthrough/go-walkthrough-fmt-55a14bbbfc53

e_factorial.go

package main
import (
    "fmt"
)
func factorial (n int) (fact int){
	
	if n==0 {
		fact=1
	}else if n<0 {
		fmt.Println("**** Factorial does not exist ****")
	}else {
		fact = n*factorial(n-1)
	}
	return fact;
}

func main() {
	var n int
	fmt.Println("Please enter a number 1-10")
	fmt.Scan(&n)
  fmt.Println("factorial is ---- ", factorial(n))
}

f_array.go

// solved problem https://www.hackerearth.com/practice/data-structures/arrays/1-d/practice-problems/algorithm/monk-and-welcome-problem/
package main 
import (
        "fmt"
    )
func main(){
    var n int;
    fmt.Scan(&n)
    var a = make([]int,n)
    var b = make([]int,n)
    for i:=0;i<n;i++{
        fmt.Scan(&a[i]);
    }
    for i:=0;i<n;i++{
        fmt.Scan(&b[i]);
        c:=a[i]+b[i]
        fmt.Printf("%v",c)
        fmt.Printf(" ")
    }
}

g_bubblesort.go

package main
import (
        "fmt"
    )
func main(){
    var n int
    fmt.Scan(&n)
    var a = make([]int,n)
    for i:=0;i<n;i++{
        fmt.Scan(&a[i]);
    }
    swap:=0
    for i:=0;i<n;i++{
        for j:=0;j<n-1;j++{
            if a[j]>a[j+1]{
                temp:=a[j]
                a[j]=a[j+1]
                a[j+1]=temp
                swap++
            }
        }
    }
    fmt.Println(swap)
}

g_palindrome.go

//https://www.hackerearth.com/practice/algorithms/string-algorithm/basics-of-string-manipulation/practice-problems/algorithm/monk-teaches-palindrome/
package main
import (
        "fmt"
    )
func reverse (b string) string{
    r := []rune(b)
    for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
		r[i], r[j] = r[j], r[i]
	}
	return string(r)
}
func isPalindrome(word string) bool {
	if word == reverse(word) {
		return true
	}
	return false
}
func checkEven(c int){
    if c%2==0 {
        fmt.Println(" EVEN")
    }else{
        fmt.Println(" ODD")
    }
}
func main(){
    var n int
    var a string
    fmt.Scan(&n)
    for i:=0;i<n;i++{
        
        fmt.Scan(&a)
        if isPalindrome(a)==true {
            fmt.Print("YES")
            checkEven(len(a))
           
        }else{
            fmt.Println("NO")
        }
    }
}

inversion.go

package main
 
import (
  "fmt"
) 
  
func travel(m [20][20]int, l int) int {
  var pairs int
  for i := 0; i < l; i++ {
    for p := i; p < l; p++ {
      for j := 0; j < l; j++ {
        for q := j; q < l; q++ {
          if m[i][j] > m[p][q] {
            pairs++
          }
        }
      }
    }
  }
  return pairs
} 
    
func main() {
  var (
    t int
    n int
    m [20][20]int 
  )
  
  fmt.Scanf("%d", &t)
    
  for i := 0; i < t; i++ {
    fmt.Scanf("%d", &n)
    for p := 0; p < n; p++ { 
      for q := 0; q < n; q++ {
        fmt.Scanf("%d", &m[p][q])
      }
    }
 
    fmt.Println(travel(m, n))
  }
}

routines.go

package main 
import (
	"fmt"
	"time"
)
func say(s string){
	for i:=0;i<5;i++{
		time.Sleep(100 * time.Millisecond)
		fmt.Printf("%v : %d \n",s, i)
		
	}
}
func main(){
	go say("Break")
	say("dance")
}

selection_sort.go

package main

import (
	"fmt"
)

func main() {
	var n int;
	fmt.Scan(&n)
	var a=make([]int,n)
	for i:=0;i<n;i++ {
		fmt.Scan(&a[i])
	}
	
	for i:=0;i<n-1;i++ {
		min:=a[i]
		for j:=i+1;j<n;j++{
			if(a[j]<min){
				min=a[j]
				a[j]=a[i]
				a[i]=min;
			}
		}
	}
	
	fmt.Println(a)
	
}

ternary_search.go

package main 
import ("fmt")
func ternarySearch(l,n ,k int ,a[] int){
	mid1:=(l+(n-l))/3
	mid2:=(n-(n-l))/3
	if a[mid1]==k{
		fmt.Println(mid1)
	}else if a[mid2]==k{
		fmt.Println(mid2)
	}else if a[k]<a[mid1]{
		ternarySearch(l,mid1-1,k,a)
	}else if a[k]>a[mid2]{
		ternarySearch(mid2+1,n,k,a)
	}else{
		ternarySearch(mid1+1,mid2-1,k,a)
	}
}

func main(){
	var n,k int
	fmt.Scan(&n,&k)
	var a=make([]int,n)
	for i:=0;i<n;i++ {
		fmt.Scan(&a[i])
	}
	l:=0
	ternarySearch(l,n-1,k,a)	


}

ydarray.go

package main 
import (
	"fmt"
	
)


func main(){

	var i,l int 
	fmt.Println("Enter row colm of array")
	fmt.Scan(&i)
	m:=make([][]int,0,0)
	for a:=0;a<i;a++{
		n:=make([]int,0,0)
		for b:=0;b<i;b++{
			fmt.Scan(&l)
			//n=append(n,l)
			n=append(n,l)
		}
		m=append(m,n)
		
	}
	fmt.Println(m)
}

zerror.go

package main 
import (
	"fmt"
	"strconv"
)


func main(){

	i, err := strconv.Atoi("42.5")
	if err != nil {
		fmt.Printf("couldn't convert number: %v\n", err)
		return
	}
	fmt.Println("Converted integer:", i)
}