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package main
import (
"database/sql"
"flag"
"fmt"
"math/rand"
"os"
"os/exec"
_ "modernc.org/sqlite"
)
var verbose = flag.Bool("v", false, "debug output")
var file = flag.String("f", "cards", "cards file")
type segmentTree struct {
N int
seg []int
}
// Build segment tree
func (s segmentTree) build(a *sql.Rows, l, r, n int) {
if l == r {
a.Next()
a.Scan(&s.seg[n])
return
}
m := (l + r) >> 1
s.build(a, l, m, n<<1)
s.build(a, m+1, r, n<<1|1)
s.seg[n] = s.seg[n<<1] + s.seg[n<<1|1]
}
// Update value at index x
func (s segmentTree) update(x, v, l, r, n int) {
if l == r {
s.seg[n] = v
return
}
m := (l + r) >> 1
if x <= m {
s.update(x, v, l, m, n<<1)
} else {
s.update(x, v, m+1, r, n<<1|1)
}
s.seg[n] = s.seg[n<<1] + s.seg[n<<1|1]
}
// Find element with prefix sum v
func (s segmentTree) query(v, l, r, n int) (int, int) {
if l == r {
return s.seg[n], l
}
m := (l + r) >> 1
if s.seg[n<<1] >= v {
return s.query(v, l, m, n<<1)
} else {
return s.query(v-s.seg[n<<1], m+1, r, n<<1|1)
}
}
func main() {
flag.Parse()
db, err := sql.Open("sqlite", *file)
if err != nil {
panic(err)
}
// Get number of cards
var N int
_ = db.QueryRow("SELECT COUNT(*) FROM cards").Scan(&N)
s := segmentTree{N, make([]int, 4*N)}
// Build segment tree
rows, err := db.Query("SELECT weight FROM cards")
if err != nil {
panic(err)
}
s.build(rows, 0, N-1, 1)
rows.Close()
if *verbose {
fmt.Println(s)
}
// https://stackoverflow.com/questions/14094190/function-similar-to-getchar
// disable input buffering
exec.Command("stty", "-F", "/dev/tty", "cbreak", "min", "1").Run()
// do not display entered characters on the screen
exec.Command("stty", "-F", "/dev/tty", "-echo").Run()
// restore the echoing state when exiting
defer exec.Command("stty", "-F", "/dev/tty", "echo").Run()
for {
// Choose a random card
x := rand.Intn(s.seg[1])
w, i := s.query(x, 0, N-1, 1)
if *verbose {
fmt.Println(x)
fmt.Println(w)
fmt.Println(i)
}
// Get card contents from database
var key, val string
db.QueryRow("SELECT key, val FROM cards WHERE idx=?", i).Scan(&key, &val)
fmt.Println(key)
// Wait for confirmation
var b []byte = make([]byte, 1)
os.Stdin.Read(b)
fmt.Println(val)
// Read user input
os.Stdin.Read(b)
if b[0] == byte('y') {
w >>= 1
} else if b[0] == byte('n') {
w <<= 1
} else {
os.Exit(0)
}
// Update segment tree and database
s.update(i, w, 0, N-1, 1)
_, err = db.Exec("UPDATE cards SET weight=? WHERE idx=?", w, i)
if err != nil {
panic(err)
}
}
}
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