LeetCode in Kotlin

567. Permutation in String

Medium

Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise.

In other words, return true if one of s1’s permutations is the substring of s2.

Example 1:

Input: s1 = “ab”, s2 = “eidbaooo”

Output: true

Explanation: s2 contains one permutation of s1 (“ba”).

Example 2:

Input: s1 = “ab”, s2 = “eidboaoo”

Output: false

Constraints:

• 1 <= s1.length, s2.length <= 104
• s1 and s2 consist of lowercase English letters.

Solution

class Solution {
    fun checkInclusion(s1: String, s2: String): Boolean {
        val n = s1.length
        val m = s2.length
        if (n > m) {
            return false
        }
        val cntS1 = IntArray(26)
        val cntS2 = IntArray(26)
        for (i in 0 until n) {
            cntS1[s1[i].code - 'a'.code]++
        }
        for (i in 0 until n) {
            cntS2[s2[i].code - 'a'.code]++
        }
        if (check(cntS1, cntS2)) {
            return true
        }
        for (i in n until m) {
            cntS2[s2[i - n].code - 'a'.code]--
            cntS2[s2[i].code - 'a'.code]++
            if (check(cntS1, cntS2)) {
                return true
            }
        }
        return false
    }

    private fun check(cnt1: IntArray, cnt2: IntArray): Boolean {
        for (i in 0..25) {
            if (cnt1[i] != cnt2[i]) {
                return false
            }
        }
        return true
    }
}

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