The bufio Package

Reading Lines with bufio.Scanner

bufio.NewScanner wraps any io.Reader and, combined with bufio.ScanLines (the default), lets you read input one line at a time by repeatedly calling Scan() and reading Text().

Example: Reading Lines with bufio.Scanner

package main

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

func main() {
	text := "line one\nline two\nline three"
	scanner := bufio.NewScanner(strings.NewReader(text))
	for scanner.Scan() {
		fmt.Println("read:", scanner.Text())
	}
}

Buffered Writing with bufio.Writer

bufio.Writer batches small writes into an internal buffer, sending them to the underlying writer in fewer, larger chunks -- which is more efficient, but requires an explicit Flush() to guarantee everything is actually written out.

Note: Always call Flush() when you're done writing, or the last buffered bytes may never reach the destination.

Example: Buffered Writing with bufio.Writer

package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	writer := bufio.NewWriter(os.Stdout)
	writer.WriteString("buffered ")
	writer.WriteString("output\n")
	writer.Flush()
	fmt.Println("flush complete")
}

Simulating Reading From Input

In a real interactive program, bufio.NewReader(os.Stdin) reads user input line by line, but since this sandbox has no live terminal input, the same bufio.Reader API is demonstrated here reading from an in-memory string instead.

Note: Judge0 has no interactive stdin, so this example simulates input with a string reader instead of os.Stdin.

Example: Simulating Reading From Input

package main

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

func main() {
	// Simulated stdin content (real os.Stdin would be used interactively)
	reader := bufio.NewReader(strings.NewReader("Gopher\n"))
	name, _ := reader.ReadString('\n')
	fmt.Println("hello,", strings.TrimSpace(name))
}