kacerrandClaude Fable 5
86a61da36f
Count paths in a map, copy into []KV, sort by count descending with cmp.Compare, truncate to n. Scanner buffer raised to 1MB for long lines; malformed lines (<3 fields) are skipped. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_012MpK9niZm4jcs3mAJbxMfi
87 lines
2.0 KiB
Go
87 lines
2.0 KiB
Go
// Exercise 04 — Log Crunching: Top-N Endpoints
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//
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// ASSIGNMENT
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// ----------
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// Log lines look like:
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//
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// 2026-08-28T10:00:01Z GET /api/users 200 123ms
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//
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// Implement TopN(r, n) so that it:
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//
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// 1. Streams the input (must handle logs far larger than memory — no
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// io.ReadAll).
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// 2. Counts requests per endpoint (3rd whitespace-separated field).
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// 3. Skips malformed lines (fewer than 3 fields) without failing.
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// 4. Handles lines longer than 64KB (hint: bufio.Scanner's default limit).
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// 5. Returns the n most frequent endpoints, most frequent first.
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// Ties: order among equal counts is unspecified.
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//
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// Run the tests: go test -race ./04-log-topn/
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package main
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import (
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"bufio"
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"cmp"
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"fmt"
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"io"
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"slices"
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"strings"
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)
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type KV struct {
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Endpoint string
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Count int
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}
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// TopN returns the n most frequent endpoints in the log stream.
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// TODO: implement me.
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func TopN(r io.Reader, n int) ([]KV, error) {
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// TODO:
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// - bufio.Scanner with an enlarged buffer
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// - map[string]int for counting
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// - copy map into []KV and sort by count desc (maps can't be sorted)
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// - truncate to n
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m := make(map[string]int)
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sc := bufio.NewScanner(r)
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sc.Buffer(make([]byte, 0, 64*1024), 1024*1024)
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for sc.Scan() {
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//fmt.Println(sc.Text())
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fields := strings.Fields(sc.Text())
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//fmt.Printf("len: %v, fields: %v\n", len(fields), fields)
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if len(fields) < 3 {
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continue
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}
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m[fields[2]]++
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}
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// copy over map into list of KV
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l := make([]KV, len(m))
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i := 0
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for k, v := range m {
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// println(i, k, v, len(l), len(m))
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l[i] = KV{k, v}
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i++
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}
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// sort by count desc
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slices.SortFunc(l, func(a, b KV) int {
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return cmp.Compare(b.Count, a.Count)
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})
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if len(l) > n {
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l = l[:n]
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}
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return l, nil
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}
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func main() {
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logs := `2026-08-28T10:00:01Z GET /api/users 200 12ms
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2026-08-28T10:00:02Z GET /api/orders 200 40ms
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2026-08-28T10:00:03Z GET /api/users 500 3ms
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garbage line
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2026-08-28T10:00:04Z POST /api/users 201 88ms`
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top, err := TopN(strings.NewReader(logs), 2)
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fmt.Println(top, err)
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}
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