LeetCode Entry

67. Add Binary

14.02.2023 easy 2023 kotlin

keep track of the overflow

67. Add Binary easy

blog post

        fun addBinary(a: String, b: String): String = StringBuilder().apply {
        var o = 0
        var i = a.lastIndex
        var j = b.lastIndex
        while (i >= 0 || j >= 0 || o == 1) {
            var num = o
            o = 0
            if (i >= 0 && a[i--] == '1') num++
            if (j >= 0 && b[j--] == '1') num++
            when (num) {
                0 -> append('0')
                1 -> append('1')
                2 -> {
                    append('0')
                    o = 1
                }
                else -> {
                    append('1')
                    o = 1
                }
            }
        }
    }.reverse().toString()

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Intuition

Scan two strings from the end and calculate the result.

Approach

• keep track of the overflow

  Complexity

• Time complexity: \(O(n)\)
• Space complexity: \(O(n)\)