6. Range

Go provides syntactic sugar to iterate easily over elements of a slice:

for INDEX, ELEMENT := range SLICE {
}

for index, element := range messages {
    // you get BOTH the index AND the element
}

The element is a copy of the value at that index.

For example:

fruits := []string{"apple", "banana", "grape"}
for i, fruit := range fruits {
    fmt.Println(i, fruit)
}
// 0 apple
// 1 banana
// 2 grape

Assignment

We need to be able to quickly detect bad words in the messages our system sends.

Complete the indexOfFirstBadWord function. If it finds any bad words in the message it should return the index of the first bad word in the msg slice. This will help us filter out naughty words from our messaging system. If no bad words are found, return -1 instead.

Use the range keyword.

Tip

Remember, you can ignore returned values with an underscore _ instead of creating an unused variable.

Solution

main.go

package main

func indexOfFirstBadWord(msg []string, badWords []string) int {
	for i, word := range msg {
		for _, bad := range badWords {
			if word == bad {
				return i // Found a bad word, return its index
			}
		}
	}
	return -1 // Only return -1 after checking ALL words
}