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Problem solution · Go

Codeforces 1530E — Minimax

Codeforces 1530E — Minimax: 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
87 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 1530E — Minimax, 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

  • 87 lines of Go from the credited upstream file 1530E.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 1530E — Minimax · GoGo
Use this to learn the idea, then write your own version.
package main import (	"bufio"	"bytes"	. "fmt"	"io"	"sort"	"strings") /* 思考记录- 全一样，直接输出- 如果有只出现一次的字母，把只出现一次且最小的放到首位，其余排序放后面（这样可以构造答案为 0 的）- 此时答案必然为 1，尝试拼凑字典序最小的：（假设 a 为最小，b 为次小，c 为第三小）  - 如果最小字母的个数-2 不超过其余字母个数：aa+其余字母排序，其余 a 间隔插入排序中的字母  - 如果只有两种字母：abb..bbaa..aa  - 如果有三种或以上的字母：abaa..aac+其余字母排序*/ // github.com/EndlessCheng/codeforces-gofunc CF1530E(_r io.Reader, _w io.Writer) {	in := bufio.NewReader(_r)	out := bufio.NewWriter(_w)	defer out.Flush() 	var T int	var s []byte	for Fscan(in, &T); T > 0; T-- {		Fscan(in, &s)		n := len(s)		cnt := [26]int{}		for _, b := range s {			cnt[b-'a']++		}		set := []int{}		pc1 := -1		for i, c := range cnt {			if c > 0 {				set = append(set, i)				if c == 1 && pc1 < 0 {					pc1 = i				}			}		}		if len(set) == 1 {			Fprintf(out, "%s\n", s)			continue		}		if pc1 >= 0 {			sort.Slice(s, func(i, j int) bool { return s[i] < s[j] })			b := 'a' + byte(pc1)			i := bytes.IndexByte(s, b)			Fprintf(out, "%c%s%s\n", b, s[:i], s[i+1:])			continue		}		cnt0 := cnt[set[0]]		b0 := 'a' + byte(set[0])		if cnt0-2 <= n-cnt0 {			Fprintf(out, "%c%c", b0, b0)			cnt0 -= 2			for _, i := range set[1:] {				for c := cnt[i]; c > 0; c-- {					Fprintf(out, "%c", 'a'+byte(i))					if cnt0 > 0 {						Fprintf(out, "%c", b0)						cnt0--					}				}			}			Fprintln(out)		} else if len(set) == 2 {			Fprintf(out, "%c%s%s\n", b0, strings.Repeat(string('a'+byte(set[1])), cnt[set[1]]), strings.Repeat(string('a'+byte(set[0])), cnt[set[0]]-1))		} else {			Fprintf(out, "%c%c%s%c", b0, 'a'+byte(set[1]), strings.Repeat(string('a'+byte(set[0])), cnt[set[0]]-1), 'a'+byte(set[2]))			cnt[set[1]]--			cnt[set[2]]--			for _, i := range set[1:] {				Fprintf(out, "%s", strings.Repeat(string('a'+byte(i)), cnt[i]))			}			Fprintln(out)		}	}} //func main() { CF1530E(os.Stdin, os.Stdout) }

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