# 20.02.2026 [761. Special Binary String]

Описание: 20.02.2026
[761. Special Binary String](https://leetcode.com/problems/special...) hard
[blog post](https://leetcode.com/problems/special...)
[substack](https://open.substack.com/pub/dmitrii...)
[youtube](   • # 20.02.2026 [761. Special Binary String]  )




#### Join me on Telegram

https://t.me/leetcode_daily_unstoppab...

#### Problem TLDR

Swaps of 1M0-special substring to make string large #hard

#### Intuition

Didn't solve :)
```j
// 30 minutes befor i go to hints
// description unclear: prefix?
// at least as many 1 as 0 what?
// 11 ok
// 01 not ok, prefix 0 has one zero and no ones
// 1010 ok
// 100 not ok, two zeros more than one
// 110 ok
// and the first condition: numbers are equal
// 1010 ok
// 1100 ok
// 101 not ok
// 110 not ok
// 10 ok
// 11101 not ok
// 11101000 ok
//
// now the swap operation to make largest possible
// meaning move ones to start
// 11011000
// **
// ****
//
//
// s length is only 50
//
// for every zero we try to:
// 1. find first substring
// 2. find next substring
//
// from zero we should only move left
//
// acceptance rate is too high 73% brainteaser?
//
// 8 minute
//
// 11011000
// **
// ****
// let's try to go only 1 position to the left
// that means next should always by 11
// followed by 00
// ok this is wrong
// 1010101100
// 1010110010 my
// 1100101010 correct
// 17 minute
// 1010101100
// aabbbb
// 1010110010 one change
// ok this can backtrack
// how many times? maybe 50? what if we just repeat
// another wrong answer
// 110110100100
// 110110100100 my
// 111010010100 correct
// so the second chunk can be longer
// 110100
// 21 minute
// we should find the shortest chunk
// or should we try all of them?
// lets just take shortest
// 30 minute wrong answer, go for hints
//101110110011010000"
//111100110100100010"
//11101001100100010"
// draw a line?? y coordinate?
```
Derived rules: starts with 1, ends with 0.
Slide and compute the balance. On each b==0 go deeper by a single char: "1(substring)0"

#### Approach

why cut and then append 1..0? To go deeper.
why can't cut 1..0 on the entire 's'? Because its not proven they are outer shell, they can be many chunks.

#### Complexity

Time complexity:
$$O(n^2)$$, can be O(n)

Space complexity:
$$O(n)$$

#### Code
https://dmitrysamoylenko.com/2023/07/...