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Problem solution · Go

Codeforces 2000H — Ksyusha and the Loaded Set

Codeforces 2000H — Ksyusha and the Loaded Set: a Go solution using direct simulation. Learn the idea, check the complexity, and read the full code, with credit to EndlessCheng Codeforces Go.

Technique
Direct simulation
Source
EndlessCheng Codeforces Go
Length
275 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Direct simulation

For Codeforces 2000H — Ksyusha and the Loaded Set, the implementation follows the problem’s operations directly while maintaining only the state needed for the next decision.

  1. Translate each rule into one explicit state update.
  2. Maintain the invariant after every processed item.
  3. Return the accumulated state once all relevant input has been handled.

Code notes

  • 275 lines of Go from the credited upstream file 2000H.go.
  • The implementation keeps its working state in language-native values and containers.
  • No explicit loop blocks detected.

Complexity

Count the number and nesting of passes over the input, then include the maintained containers in the memory estimate.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from EndlessCheng Codeforces Go by Σndless (EndlessCheng) and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeCodeforces 2000H — Ksyusha and the Loaded Set · GoGo
Use this to learn the idea, then write your own version.
package main import (	"bufio"	"cmp"	. "fmt"	"io") // https://github.com/EndlessChengtype nodeMS00[K comparable] struct {	son      [2]*nodeMS00[K]	priority uint	key      K	keyCnt   int	subSize  int} func (o *nodeMS00[K]) size() int {	if o != nil {		return o.subSize	}	return 0} func (o *nodeMS00[K]) maintain() {	o.subSize = o.keyCnt + o.son[0].size() + o.son[1].size()} func (o *nodeMS00[K]) rotate(d int) *nodeMS00[K] {	x := o.son[d^1]	o.son[d^1] = x.son[d]	x.son[d] = o	o.maintain()	x.maintain()	return x} type treapMS00[K comparable] struct {	rd         uint	root       *nodeMS00[K]	comparator func(a, b K) int} func (t *treapMS00[K]) fastRand() uint {	t.rd ^= t.rd << 13	t.rd ^= t.rd >> 17	t.rd ^= t.rd << 5	return t.rd} func (t *treapMS00[K]) empty() bool { return t.root.size() == 0 } func (t *treapMS00[K]) _put(o *nodeMS00[K], key K) *nodeMS00[K] {	if o == nil {		o = &nodeMS00[K]{priority: t.fastRand(), key: key, keyCnt: 1}	} else {		c := t.comparator(key, o.key)		if c == 0 {			o.keyCnt++		} else {			d := 0			if c > 0 {				d = 1			}			o.son[d] = t._put(o.son[d], key)			if o.son[d].priority > o.priority {				o = o.rotate(d ^ 1)			}		}	}	o.maintain()	return o} func (t *treapMS00[K]) put(key K) { t.root = t._put(t.root, key) } func (t *treapMS00[K]) _delete(o *nodeMS00[K], key K) *nodeMS00[K] {	if o == nil {		return nil	}	if c := t.comparator(key, o.key); c != 0 {		d := 0		if c > 0 {			d = 1		}		o.son[d] = t._delete(o.son[d], key)	} else {		if o.keyCnt > 1 {			o.keyCnt--		} else {			if o.son[1] == nil {				return o.son[0]			}			if o.son[0] == nil {				return o.son[1]			}			d := 0			if o.son[0].priority > o.son[1].priority {				d = 1			}			o = o.rotate(d)			o.son[d] = t._delete(o.son[d], key)		}	}	o.maintain()	return o} func (t *treapMS00[K]) delete(key K) { t.root = t._delete(t.root, key) } func (t *treapMS00[K]) min() *nodeMS00[K] { return t.kth(0) } func (t *treapMS00[K]) lowerBoundIndex(key K) (kth int) {	for o := t.root; o != nil; {		c := t.comparator(key, o.key)		if c < 0 {			o = o.son[0]		} else if c > 0 {			kth += o.son[0].size() + o.keyCnt			o = o.son[1]		} else {			kth += o.son[0].size()			break		}	}	return} func (t *treapMS00[K]) kth(k int) (o *nodeMS00[K]) {	if k < 0 || k >= t.root.size() {		return	}	for o = t.root; o != nil; {		leftSize := o.son[0].size()		if k < leftSize {			o = o.son[0]		} else {			k -= leftSize + o.keyCnt			if k < 0 {				break			}			o = o.son[1]		}	}	return} func newMultiset00[K cmp.Ordered]() *treapMS00[K] {	return &treapMS00[K]{		rd:         1,		comparator: cmp.Compare[K],	}} const stNodeDefaultVal00 = 1e9 var emptyStNode00 = &stNode00{val: stNodeDefaultVal00} func init() {	emptyStNode00.lo = emptyStNode00	emptyStNode00.ro = emptyStNode00} type stNode00 struct {	lo, ro    *stNode00	l, r, val int} func (o *stNode00) update(i int, val int) {	if o.l == o.r {		o.val = val		return	}	m := (o.l + o.r) >> 1	if i <= m {		if o.lo == emptyStNode00 {			o.lo = &stNode00{lo: emptyStNode00, ro: emptyStNode00, l: o.l, r: m, val: stNodeDefaultVal00}		}		o.lo.update(i, val)	} else {		if o.ro == emptyStNode00 {			o.ro = &stNode00{lo: emptyStNode00, ro: emptyStNode00, l: m + 1, r: o.r, val: stNodeDefaultVal00}		}		o.ro.update(i, val)	}	o.val = min(o.lo.val, o.ro.val)} func (o *stNode00) query(l int) int {	if o == emptyStNode00 || l > o.r {		return stNodeDefaultVal00	}	if l <= o.l {		return o.val	}	return min(o.lo.query(l), o.ro.query(l))} func newStRoot00(l, r int) *stNode00 {	return &stNode00{lo: emptyStNode00, ro: emptyStNode00, l: l, r: r, val: stNodeDefaultVal00}} func cf2000H(in io.Reader, _w io.Writer) {	out := bufio.NewWriter(_w)	defer out.Flush()	const mx = 4e6 + 1	var T, n, v, m int	var op string	for Fscan(in, &T); T > 0; T-- {		t := newStRoot00(1, mx)		gap := map[int]*treapMS00[int]{}		put := func(l, r int) {			k := r - l - 1			if k == 0 {				return			}			if gap[k] == nil {				gap[k] = newMultiset00[int]()			}			gap[k].put(l + 1)			t.update(k, gap[k].min().key)		}		del := func(l, r int) {			k := r - l - 1			if k == 0 {				return			}			t2 := gap[k]			t2.delete(l + 1)			if t2.empty() {				t.update(k, 1e9)			} else {				t.update(k, t2.min().key)			}		} 		set := newMultiset00[int]()		set.put(0)		pre := 0		for Fscan(in, &n); n > 0; n-- {			Fscan(in, &v)			set.put(v)			put(pre, v)			pre = v		}		set.put(mx)		put(pre, mx) 		for Fscan(in, &m); m > 0; m-- {			Fscan(in, &op, &v)			if op == "+" {				i := set.lowerBoundIndex(v)				l, r := set.kth(i-1).key, set.kth(i).key				set.put(v)				del(l, r)				put(l, v)				put(v, r)			} else if op == "-" {				i := set.lowerBoundIndex(v)				l, r := set.kth(i-1).key, set.kth(i+1).key				set.delete(v)				del(l, v)				del(v, r)				put(l, r)			} else {				Fprint(out, t.query(v), " ")			}		}		Fprintln(out)	}} //func main() { cf2000H(bufio.NewReader(os.Stdin), os.Stdout) }

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