sort: use fmt.Scan in ExampleSearch_guessingGame to handle leftover n…

[AkariH]

What does this PR do?

This PR fixes an interactive input glitch in ExampleSearch_guessingGame within the sort.Search documentation example in src/sort/search.go.

Root Cause & Problem

Currently, ExampleSearch_guessingGame uses fmt.Scanf("%s", &s) inside the binary search closure passed to sort.Search:

func GuessingGame() {
    var s string
    fmt.Printf("Pick an integer from 0 to 100.\n")
    answer := sort.Search(100, func(i int) bool {
        fmt.Printf("Is your number <= %d? ", i)
        fmt.Scanf("%s", &s)
        return s != "" && s[0] == 'y'
    })
    fmt.Printf("Your number is %d.\n", answer)
}

When executed in a real interactive TTY session:

1. Entering 'y' followed by Enter leaves the newline character '\n' in os.Stdin's buffer.
2. In subsequent binary search iterations of sort.Search, fmt.Scanf("%s", &s) reads the leftover '\n', fails to parse a non-empty string token, and returns immediately without waiting for keyboard input.
3. As a result, all remaining interactive prompts in the search process are skipped without user interaction.

Solution

Replace fmt.Scanf("%s", &s) with fmt.Scan(&s).

fmt.Scan automatically consumes and discards leading whitespace and newline characters ('\n'), ensuring that each iteration correctly blocks and waits for user input.

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