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Problem solution · Go

Codeforces 1771F — Hossam and Range Minimum Query

Codeforces 1771F — Hossam and Range Minimum Query: 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
90 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 1771F — Hossam and Range Minimum Query, 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

  • 90 lines of Go from the credited upstream file 1771F.go.
  • The implementation visibly relies on sequence storage.
  • 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 1771F — Hossam and Range Minimum Query · GoGo
Use this to learn the idea, then write your own version.
package main import (	"bufio"	. "fmt"	"io"	"math/rand"	"runtime/debug"	"time") // https://space.bilibili.com/206214var null = &node71{} func init() {	debug.SetGCPercent(-1)	null.lo = null	null.ro = null} type node71 struct {	lo, ro *node71	xorS   int} func (o node71) modify(l, r, i int, v int) *node71 {	if l == r {		o.xorS ^= v		return &o	}	m := (l + r) >> 1	if i <= m {		if o.lo == null {			o.lo = &node71{lo: null, ro: null}		}		o.lo = o.lo.modify(l, m, i, v)	} else {		if o.ro == null {			o.ro = &node71{lo: null, ro: null}		}		o.ro = o.ro.modify(m+1, r, i, v)	}	o.xorS = o.lo.xorS ^ o.ro.xorS	return &o} func (o *node71) query(old *node71, l, r int) int {	if l == r {		return l	}	m := (l + r) >> 1	if o.lo.xorS != old.lo.xorS {		return o.lo.query(old.lo, l, m)	}	return o.ro.query(old.ro, m+1, r)} func cf1771F(_r io.Reader, _w io.Writer) {	in := bufio.NewReader(_r)	out := bufio.NewWriter(_w)	defer out.Flush()	rand.Seed(time.Now().UnixNano())	const R int = 1e9 + 1 	var n, v, q, l, r, ans int	Fscan(in, &n)	t := make([]*node71, n+1)	t[0] = &node71{lo: null, ro: null}	mp := make(map[int]int, n)	for i := 1; i <= n; i++ {		Fscan(in, &v)		if _, ok := mp[v]; !ok {			mp[v] = rand.Int()		}		t[i] = t[i-1].modify(0, R, v, mp[v])	}	for Fscan(in, &q); q > 0; q-- {		Fscan(in, &l, &r)		l ^= ans		r ^= ans		ans = t[r].query(t[l-1], 0, R)		if ans > 1e9 {			ans = 0		}		Fprintln(out, ans)	}} //func main() { cf1771F(os.Stdin, os.Stdout) }

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