LeetCode Entry

1653. Minimum Deletions to Make String Balanced

07.02.2026 medium 2026 kotlin rust

Min removal to balance 'ab'

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Problem TLDR

Min removal to balance ‘ab’ #medium #greedy

Intuition

Split at each position and compare left and right counts of ‘a’ and ‘b’. The greedy intuition: count ‘b’, at each ‘a’ choose min of (remove ‘a’=d+1, keep ‘a’=b count removed)

Approach

• the corner cases of single ‘a’ and ‘b’ should be checked

Complexity

• Time complexity: \(O(n)\)

• Space complexity: \(O(1)\)

Code

// 24ms
    fun minimumDeletions(s: String): Int {
        var b = 0
        return min(0,s.minOf { b += 2*(it - 'a')-1; b }) + s.count{it=='a'}
    }

// 10ms
    pub fn minimum_deletions(s: String) -> i32 {
        s.bytes().fold((0,0),|(b,d),c|if c>b'a'{(b+1,d)}else{(b,b.min(d+1))}).1
    }