Use struct for segmentTree

Changes

1 changed files (+28/-24)

• sd.go
  • @@ -14,45 +14,49 @@
    var verbose = flag.Bool("v", false, "debug output") var file = flag.String("f", "cards", "cards file") - var sum = 0 - var seg = []int{} + type segmentTree struct { + N int + seg []int + } - func build(a *sql.Rows, l, r, n int) { + // Build segment tree + func (s segmentTree) build(a *sql.Rows, l, r, n int) { if l == r { a.Next() - a.Scan(&seg[n]) - sum += seg[n] + a.Scan(&s.seg[n]) return } m := (l + r) >> 1 - build(a, l, m, n<<1) - build(a, m+1, r, n<<1|1) - seg[n] = seg[n<<1] + seg[n<<1|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] } - func update(x, v, l, r, n int) { + // Update value at index x + func (s segmentTree) update(x, v, l, r, n int) { if l == r { - seg[n] = v + s.seg[n] = v return } m := (l + r) >> 1 if x <= m { - update(x, v, l, m, n<<1) + s.update(x, v, l, m, n<<1) } else { - update(x, v, m+1, r, n<<1|1) + s.update(x, v, m+1, r, n<<1|1) } - seg[n] = seg[n<<1] + seg[n<<1|1] + s.seg[n] = s.seg[n<<1] + s.seg[n<<1|1] } - func query(v, l, r, n int) (int, int) { + // Find element with prefix sum v + func (s segmentTree) query(v, l, r, n int) (int, int) { if l == r { - return seg[n], l + return s.seg[n], l } m := (l + r) >> 1 - if seg[n<<1] >= v { - return query(v, l, m, n<<1) + if s.seg[n<<1] >= v { + return s.query(v, l, m, n<<1) } else { - return query(v-seg[n<<1], m+1, r, n<<1|1) + return s.query(v-s.seg[n<<1], m+1, r, n<<1|1) } }
  • @@ -67,19 +71,19 @@
    // Get number of cards var N int _ = db.QueryRow("SELECT COUNT(*) FROM cards").Scan(&N) - seg = make([]int, 4*N) + s := segmentTree{N, make([]int, 4*N)} // Build segment tree rows, err := db.Query("SELECT weight FROM cards") if err != nil { panic(err) } - build(rows, 0, N-1, 1) + s.build(rows, 0, N-1, 1) + sum := s.seg[1] rows.Close() if *verbose { - fmt.Println(N) - fmt.Println(seg) + fmt.Println(s) } // https://stackoverflow.com/questions/14094190/function-similar-to-getchar
  • @@ -97,7 +101,7 @@ if *verbose {
    fmt.Println(sum) fmt.Println(x) } - w, i := query(x, 0, N-1, 1) + w, i := s.query(x, 0, N-1, 1) fmt.Println(w) fmt.Println(i)
  • @@ -124,7 +128,7 @@ os.Exit(0)
    } // Update segment tree and database - update(i, w, 0, N-1, 1) + s.update(i, w, 0, N-1, 1) _, err = db.Exec("UPDATE cards SET weight=? WHERE idx=?", w, i) if err != nil { panic(err)