Go Program to Count Words in String

In Go, you can count words in a string by using strings.Fields(yourString) to split the string into words and then get the length with len(), like wordCount := len(strings.Fields(yourString)).

Examples

InputHello world

Output2

InputGo is fun to learn

Output5

Input

Output0

How to Think About It

To count words in a string, first split the string into parts separated by spaces or other whitespace. Each part is a word. Then count how many parts you have. This works because words are usually separated by spaces.

Algorithm

1

Get the input string.

2

Split the string into words using whitespace as separator.

3

Count the number of words obtained.

4

Return or print the count.

Code

go

package main

import (
	"fmt"
	"strings"
)

func main() {
	text := "Go is fun to learn"
	words := strings.Fields(text)
	count := len(words)
	fmt.Println(count)
}

Output

5

Dry Run

Let's trace the string "Go is fun to learn" through the code

1

Input string

text = "Go is fun to learn"

2

Split string into words

words = ["Go", "is", "fun", "to", "learn"]

3

Count words

count = 5

4

Print count

Output: 5

Iteration	Word
1	Go
2	is
3	fun
4	to
5	learn

Why This Works

Step 1: Splitting the string

The strings.Fields function splits the input string into a slice of words by whitespace.

Step 2: Counting words

The len() function returns the number of elements in the slice, which equals the number of words.

Step 3: Outputting the result

Printing the count shows how many words the input string contains.

Alternative Approaches

Manual loop with rune check

go

package main

import (
	"fmt"
	"unicode"
)

func countWords(s string) int {
	inWord := false
	count := 0
	for _, r := range s {
		if unicode.IsSpace(r) {
			inWord = false
		} else if !inWord {
			inWord = true
			count++
		}
	}
	return count
}

func main() {
	text := "Go is fun to learn"
	fmt.Println(countWords(text))
}

This method manually checks each character to count words, useful if you want more control but is more complex.

Using bufio.Scanner

go

package main

import (
	"bufio"
	"fmt"
	"strings"
)

func main() {
	text := "Go is fun to learn"
	scanner := bufio.NewScanner(strings.NewReader(text))
	scanner.Split(bufio.ScanWords)
	count := 0
	for scanner.Scan() {
		count++
	}
	fmt.Println(count)
}

Using bufio.Scanner with ScanWords splits words efficiently, good for large input streams.

Complexity: O(n) time, O(n) space

Time Complexity

The program scans each character once to split words, so time grows linearly with input size.

Space Complexity

Splitting creates a slice holding all words, so space also grows linearly with input size.

Which Approach is Fastest?

Using strings.Fields is simple and fast for most cases; manual rune checking is slower but more flexible; bufio.Scanner is efficient for streaming large text.

Approach	Time	Space	Best For
strings.Fields	O(n)	O(n)	Simple and small to medium strings
Manual rune check	O(n)	O(1)	Custom word definitions or low memory
bufio.Scanner	O(n)	O(n)	Large input streams or files