Last Word

Last word is a function that takes a string and return the last word of that string.

Last Word step by step

First step

We set 3 variables: - Start as an int that will be the index of the beggining of our last word.
- End as an int for the index of the ending of our last word.
- condition as a boolean set to true that will be used to detect if we had our start value or not.

start := 0
end := 0
condition := true

Second step

We loop over our string backwards

for i := len(s) - 1; i >= 0; i-- {
}

Since we're gonna use i as an index, we need to start at len(s) - 1 to avoid getting an out of range error.

Third step

We then setup 2 conditions, one for the start index, the other one for the end index.

First condition we check if the boolean is still true and if our current letter isn't a space.
Once we found a letter we give to end the value of i and we set the boolean value to false to make sure it won't change that value again.

if s[i] != ' ' && condition {
    end = i
    condition = false
}

Second condition we check the end of the word by looking for a space.
Once found we give start the value of i and set i to 0 to end the loop.

else if s[i] == ' ' && !condition {
    start = i
    i = 0
}

We then have this:

for i := len(s) - 1; i >= 0; i-- {
    // condition for the end index
        if s[i] != ' ' && condition {
            end = i
            condition = false
      // condition for the start index
        } else if s[i] == ' ' && !condition {
            start = i
            i = 0
        }
    }

Fourth and final step

Once we have index of the start and end of that last word, we can return it using:

return s[start:end+1] + "\n"

The reason you need to use end+1 is because of how Go handles string slicing. If we use only end, we will miss a letter because the index end is not included.

Full code

func lastword(s string) string {
  // first step
    start := 0
    end := 0
    condition := true
  // second step
    for i := len(s) - 1; i >= 0; i-- {
    // third step
        if s[i] != ' ' && condition {
            end = i
            condition = false
        } else if s[i] == ' ' && !condition {
            start = i
            i = 0
        }
    }
  // last step
    return s[start:end+1] + "\n"
}