Hi I am trying to find the no. of times a digit appears in a no. using the below code. But the value of j is always 0 even if the digit appears many time in the number. I would like to know why the current comparison does not work. Is it possible to do this without converting input to integer?
package main
import "fmt"
import "bufio"
import "os"
func main (){
reader := bufio.NewReader(os.Stdin)
c,_ := reader.ReadString('\n')
d,_ := reader.ReadString('\n')
j := 0
for _,i := range(c){
if string(i) == d{
fmt.Printf("inside if")
j = j+1
}
}
fmt.Println(j)
}
func (b *Reader) ReadString(delim byte) (string, error)
ReadString reads until the first occurrence of delim in the input, returning a string containing the data up to and including the delimiter.
So if you enter 3 for d, then d == "3\n".
You probably just need to do:
d,_ := reader.ReadString('\n')
d = d[:len(d)-1]
Related
I have a string like this:
package main
import "fmt"
func main() {
some := "p1k4"
for i, j := range some {
fmt.Println()
}
}
I want take each two consecutive characters in the string and print them. the output should like p1, 1k, k4, 4p.
I have tried it and still having trouble finding the answer, how should I write the code in go and get the output I want?
Go stores strings in memory as their UTF-8 encoded byte sequence. This maps ASCII charactes one-to-one in bytes, but characters outside of that range map to multiple bytes.
So I would advise to use the for range loop over a string, which ranges over the runes (characters) of the string, properly decoding multi-byte runes. This has the advantage that it does not require allocation (unlike converting the string to []rune). You may also print the pairs using fmt.Printf("%c%c", char1, char2), which also will not require allocation (unlike converting runes back to string and concatenating them).
To learn more about strings, characters and runes in Go, read blog post: Strings, bytes, runes and characters in Go
Since the loop only returns the "current" rune in the iteration (but not the previous or the next rune), use another variable to store the previous (and first) runes so you have access to them when printing.
Let's write a function that prints the pairs as you want:
func printPairs(s string) {
var first, prev rune
for i, r := range s {
if i == 0 {
first, prev = r, r
continue
}
fmt.Printf("%c%c, ", prev, r)
prev = r
}
// Print last pair: prev is the last rune
fmt.Printf("%c%c\n", prev, first)
}
Testing it with your input and with another string that has multi-byte runes:
printPairs("p1k4")
printPairs("Go-世界")
Output will be (try it on the Go Playground):
p1, 1k, k4, 4p
Go, o-, -世, 世界, 界G
package main
import (
"fmt"
)
func main() {
str := "12345"
for i := 0; i < len(str); i++ {
fmt.Println(string(str[i]) + string(str[(i+1)%len(str)]))
}
}
This is a simple for loop over your string with the first character appended at the back:
package main
import "fmt"
func main() {
some := "p1k4"
ns := some + string(some[0])
for i := 0; i < len(ns)-1; i++ {
fmt.Println(ns[i:i+2])
}
}
I currently have a script that performs an os command, that returns a great deal of data, at the end of the data it gives a total such that:
N Total.
N can be any number from 0 upward.
I want to perform this command, and take N then put it into a value. I have the command running and I'm storing it in a bytes.Buffer, however I'm unsure how to scrape this so that I only get the number. The "N Total." string is always at the end of the output. Any help would be appreciated as I've seen various different methods but they all seem quite convoluted.
You can use a bufio.Scanner to read the command's output line-wise. Then just remember the last line and parse it once the command has finished.
package main
import (
"bufio"
"fmt"
"io"
"os/exec"
"strings"
)
func main() {
r, w := io.Pipe()
cmd := exec.Command("fortune")
cmd.Stdout = w
go func() {
cmd.Run()
r.Close()
w.Close()
}()
sc := bufio.NewScanner(r)
var lastLine string
for sc.Scan() {
line := sc.Text()
fmt.Println("debug:", line)
if strings.TrimSpace(line) != "" {
lastLine = line
}
}
fmt.Println(lastLine)
}
Sample output:
debug: "Get back to your stations!"
debug: "We're beaming down to the planet, sir."
debug: -- Kirk and Mr. Leslie, "This Side of Paradise",
debug: stardate 3417.3
stardate 3417.3
Parsing lastLine is left as an excercise for the reader.
You can split the string by \n and get the last line.
package main
import (
"fmt"
"strconv"
"strings"
)
func main() {
output := `
Some os output
Some more os output
Again some os output
1001 Total`
// If you're getting the string from the bytes.Buffer do this:
// output := myBytesBuffer.String()
outputSplit := strings.Split(output, "\n") // Break into lines
// Get last line from the end.
// -1 assumes the numbers in the last line. Change it if its not.
lastLine := outputSplit[len(outputSplit)-1]
lastLine = strings.Replace(lastLine, " Total", "", -1) // Remove text
number, _ := strconv.Atoi(lastLine) // Convert from text to number
fmt.Println(number)
}
peterSO points out that for big output the above may be slow.
Here's another way that uses a compiled regexp expression to match against a small subset of bytes.
package main
import (
"bytes"
"fmt"
"os/exec"
"regexp"
"strconv"
)
func main() {
// Create regular expression. You only create this once.
// Would be regexpNumber := regexp.MustCompile(`(\d+) Total`) for you
regexpNumber := regexp.MustCompile(`(\d+) bits physical`)
// Whatever your os command is
command := exec.Command("cat", "/proc/cpuinfo")
output, _ := command.Output()
// Your bytes.Buffer
var b bytes.Buffer
b.Write(output)
// Get end of bytes slice
var end []byte
if b.Len()-200 > 0 {
end = b.Bytes()[b.Len()-200:]
} else {
end = b.Bytes()
}
// Get matches. matches[1] contains your number
matches := regexpNumber.FindSubmatch(end)
// Convert bytes to int
number, _ := strconv.Atoi(string(matches[1])) // Convert from text to number
fmt.Println(number)
}
I know that for counting the occurrence of one substring I can use "strings.Count(, )". What if I want to count the number of occurrences of substring1 OR substring2? Is there a more elegant way than writing another new line with strings.count()?
Use a regular expression:
https://play.golang.org/p/xMsHIYKtkQ
aORb := regexp.MustCompile("A|B")
matches := aORb.FindAllStringIndex("A B C B A", -1)
fmt.Println(len(matches))
Another way to do substring matching is with the suffixarray package. Here is an example of matching multiple patterns:
package main
import (
"fmt"
"index/suffixarray"
"regexp"
)
func main() {
r := regexp.MustCompile("an")
index := suffixarray.New([]byte("banana"))
results := index.FindAllIndex(r, -1)
fmt.Println(len(results))
}
You can also match a single substring with the Lookup function.
If you want to count the number of matches in a large string, without allocating space for all the indices just to get the length and then throwing them away, you can use Regexp.FindStringIndex in a loop to match against successive substrings:
func countMatches(s string, re *regexp.Regexp) int {
total := 0
for start := 0; start < len(s); {
remaining := s[start:] // slicing the string is cheap
loc := re.FindStringIndex(remaining)
if loc == nil {
break
}
// loc[0] is the start index of the match,
// loc[1] is the end index (exclusive)
start += loc[1]
total++
}
return total
}
func main() {
s := "abracadabra"
fmt.Println(countMatches(s, regexp.MustCompile(`a|b`)))
}
runnable example at Go Playground
Let's say for example that I have one string, like this:
<h1>Hello World!</h1>
What Go code would be able to extract Hello World! from that string? I'm still relatively new to Go. Any help is greatly appreciated!
If the string looks like whatever;START;extract;END;whatever you can use this which will get the string in between:
// GetStringInBetween Returns empty string if no start string found
func GetStringInBetween(str string, start string, end string) (result string) {
s := strings.Index(str, start)
if s == -1 {
return
}
s += len(start)
e := strings.Index(str[s:], end)
if e == -1 {
return
}
e += s + e - 1
return str[s:e]
}
What happens here is it will find first index of START, adds length of START string and returns all that exists from there until first index of END.
There are lots of ways to split strings in all programming languages.
Since I don't know what you are especially asking for I provide a sample way to get the output
you want from your sample.
package main
import "strings"
import "fmt"
func main() {
initial := "<h1>Hello World!</h1>"
out := strings.TrimLeft(strings.TrimRight(initial,"</h1>"),"<h1>")
fmt.Println(out)
}
In the above code you trim <h1> from the left of the string and </h1> from the right.
As I said there are hundreds of ways to split specific strings and this is only a sample to get you started.
Hope it helps, Good luck with Golang :)
DB
I improved the Jan Kardaš`s answer.
now you can find string with more than 1 character at the start and end.
func GetStringInBetweenTwoString(str string, startS string, endS string) (result string,found bool) {
s := strings.Index(str, startS)
if s == -1 {
return result,false
}
newS := str[s+len(startS):]
e := strings.Index(newS, endS)
if e == -1 {
return result,false
}
result = newS[:e]
return result,true
}
Here is my answer using regex. Not sure why no one suggested this safest approach
package main
import (
"fmt"
"regexp"
)
func main() {
content := "<h1>Hello World!</h1>"
re := regexp.MustCompile(`<h1>(.*)</h1>`)
match := re.FindStringSubmatch(content)
if len(match) > 1 {
fmt.Println("match found -", match[1])
} else {
fmt.Println("match not found")
}
}
Playground - https://play.golang.org/p/Yc61x1cbZOJ
In the strings pkg you can use the Replacer to great affect.
r := strings.NewReplacer("<h1>", "", "</h1>", "")
fmt.Println(r.Replace("<h1>Hello World!</h1>"))
Go play!
func findInString(str, start, end string) ([]byte, error) {
var match []byte
index := strings.Index(str, start)
if index == -1 {
return match, errors.New("Not found")
}
index += len(start)
for {
char := str[index]
if strings.HasPrefix(str[index:index+len(match)], end) {
break
}
match = append(match, char)
index++
}
return match, nil
}
Read up on the strings package. Have a look into the SplitAfter function which can do something like this:
var sample = "[this][is my][string]"
t := strings.SplitAfter(sample, "[")
That should produce a slice something like: "[", "this][", "is my][", "string]". Using further functions for Trimming you should get your solution. Best of luck.
func Split(str, before, after string) string {
a := strings.SplitAfterN(str, before, 2)
b := strings.SplitAfterN(a[len(a)-1], after, 2)
if 1 == len(b) {
return b[0]
}
return b[0][0:len(b[0])-len(after)]
}
the first call of SplitAfterN will split the original string into array of 2 parts divided by the first found after string, or it will produce array containing 1 part equal to the original string.
second call of SplitAfterN uses a[len(a)-1] as input, as it is "the last item of array a". so either string after after or the original string str. the input will be split into array of 2 parts divided by the first found before string, or it will produce array containing 1 part equal to the input.
if after was not found than we can simply return b[0] as it is equal to a[len(a)-1]
if after is found, it will be included at the end of b[0] string, therefore you have to trim it via b[0][0:len(b[0])-len(after)]
all strings are case sensitive
i have the following code:
I know about runes in go, i read about them a lot in the last hours i have tried to solve this...
package main
import (
"fmt"
"strconv"
)
func main() {
e := "\x002"
fmt.Println(e)
new := string(e)
i, err := strconv.Atoi(new)
if err != nil { fmt.Println(err) }
fmt.Println(i)
}
result is:
2
strconv.ParseInt: parsing "\x002": invalid syntax
0
why can't i convert the string to an integer?
Any help appreciated!
I'm not 100% sure of your goal but it looks like you want to extract the int value of the rune you get from a string containing a given character.
It looks like you want
e := "\x02"
runes := []rune(e)
i := runes[0]
fmt.Println(i) // 2
\xXXXX tries to parse it as a unicode rune, you need to skip the \ check this:
Either use :
e := "\\x002"
#or use a raw string :
e := `\x002`
edit :
Why do you think \x002 is a valid integer? do you mean 0x002?