How to compare a character with the next one in the same string

Question

I am struggling a bit on how to operate with strings. Furthermore, apparently there is no "while" loops, there are only "for" loops, which doesn't allow me to achieve what I want. Basically, given the string: "helloujjkk" I want to compare all characters with the next one, and to verify if they match. Example, for "helloujjkk", I want to return "l","j", and "k" because those characters are followed by the same character. The way I did this in Python was like this:

hello="helloujjkk"
i=0
while i < len(hello)-1:
    if hello[i] == hello[i+1]:
        print hello[i]
    i +=1

So far, this is the way I am iterating over the string:

word := "helloujjkk"
for _,character := range word {
     fmt.Println(string(character))
}

but I haven't found how can I find the "next" character in the string.

Answer 1

You can do the same thing you did in Python:

word := "helloujjkk"
for i:=0;i<len(word)-1;i++ {
    if word[i]==word[i+1] {
       fmt.Println(string(word[i]))
    }
}

However, this will break if your word contains multibyte characters. String indexing in Go treats the string as an array of bytes, so word[i] is the i'th byte of the string. This is not necessarily the i'th character.

A better solution would be to keep the last character read from the string:

var last rune
for i,c:=range word {
   if i>0 && c==last {
      fmt.Println(string(c))
   }
   last=c
   }
}

A range over a string will iterate the runes of the string, not the bytes. So this version is correct even if the string contains multibyte characters.