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Problem solution · Go

Codeforces 1468M — Similar Sets

Codeforces 1468M — Similar Sets: 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
168 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 1468M — Similar Sets, 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

  • 168 lines of Go from the credited upstream file 1468M.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 1468M — Similar Sets · GoGo
Use this to learn the idea, then write your own version.
package main import (	"bufio"	. "fmt"	"io"	"math"	"sort") // github.com/EndlessCheng/codeforces-gofunc CF1468M(_r io.Reader, _w io.Writer) {	in := bufio.NewReader(_r)	out := bufio.NewWriter(_w)	defer out.Flush() 	var T, n, m, v into:	for Fscan(in, &T); T > 0; T-- {		Fscan(in, &n)		nn := n		a := make([][]int, n)		vid := map[int]int{}		for i := range a {			Fscan(in, &m)			a[i] = make([]int, m)			for j := range a[i] {				Fscan(in, &v)				if vid[v] == 0 {					vid[v] = n					n++				}				a[i][j] = vid[v]			}		}		g := make([][]int, n)		deg := make([]int, n)		for v, r := range a {			for _, w := range r {				g[v] = append(g[v], w)				g[w] = append(g[w], v)				deg[v]++				deg[w]++			}		}		less := func(v, w int) bool { return deg[v] < deg[w] || deg[v] == deg[w] && v < w } 		g2 := make([][]int, n)		for v, ws := range g {			for _, w := range ws {				if less(v, w) {					g2[v] = append(g2[v], w)				}			}		}		id := make([]int, n)		for v, ws := range g {			for _, w := range ws {				for _, u := range g2[w] {					if less(v, u) {						if id[u] > 0 {							if v < nn {								Fprintln(out, v+1, u+1)							} else {								Fprintln(out, w+1, id[u])							}							continue o						}						id[u] = w + 1					}				}			}			for _, w := range ws {				for _, u := range g2[w] {					if less(v, u) {						id[u] = 0					}				}			}		}		Fprintln(out, -1)	}} // 分块解法func CF1468M2(_r io.Reader, _w io.Writer) {	in := bufio.NewReader(_r)	out := bufio.NewWriter(_w)	defer out.Flush()	type pair struct{ v, i int } 	var T, n, m, v into:	for Fscan(in, &T); T > 0; T-- {		Fscan(in, &n)		a := make([][]int, n)		vid := map[int]int{}		for i := range a {			Fscan(in, &m)			a[i] = make([]int, m)			for j := range a[i] {				Fscan(in, &v)				if _, has := vid[v]; !has {					vid[v] = len(vid)				}				a[i][j] = vid[v]			}		} 		n = len(vid)		sz := int(math.Round(math.Sqrt(float64(n)) / 3)) // 不能直接用 sqrt(n)，会 MLE，测试发现 /3 比较适合 		has := make([]int, n)		for i, b := range a {			if len(b) < sz {				continue			}			for _, v := range b {				has[v] = i + 1			}			for j, c := range a {				if j == i {					continue				}				found := false				for _, v := range c {					if has[v] == i+1 {						if found {							Fprintln(out, i+1, j+1)							continue o						}						found = true					}				}			}		} 		// 这种写法比 map 更省内存		groups := make([][]pair, n)		for i, b := range a {			if len(b) < sz {				sort.Ints(b)				for j, v := range b {					for _, w := range b[:j] {						groups[v] = append(groups[v], pair{w, i + 1})					}				}			}		}		id := make([]int, n)		for _, g := range groups {			for _, p := range g {				if id[p.v] > 0 {					Fprintln(out, id[p.v], p.i)					continue o				}				id[p.v] = p.i			}			for _, p := range g {				id[p.v] = 0			}		}		Fprintln(out, -1)	}} //func main() { CF1468M(os.Stdin, os.Stdout) }

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