LeetCode3.滑动窗口: 双指针法(Kotlin语言)-无重复字符的最长子串

/**
 * 暴力破解法: 遍历所有子串,会出现超时 LTE
 */
fun lengthOfLongestSubstring(s: String): Int {
    var ans = 0
    // 遍历所有子串
    val charArray = s.toCharArray()
    val n = charArray.size
    if (n == 0) return 0
    for (i in 0 until n) {
        for (j in i..n) {
            val substr = s.substring(i, j)
            if (isUniqString(substr)) {
                ans = Math.max(ans, substr.length)
            }
        }
    }
    return ans
}

/**
 * 判断字符串中的字符是否全部无重复
 */
fun isUniqString(s: String): Boolean {
    val charArray = s.toCharArray()
    val len1 = charArray.size
    val len2 = charArray.groupBy { it }.keys.size
    return len1 == len2
}

class Solution {
    fun lengthOfLongestSubstring(s: String): Int {
        var ans = 0
        var left = 0
        var right = 0
        val n = s.length

        val window = mutableSetOf<Char>()

        while (left < n && right < n) {
            // slide right pointer
            if (!window.contains(s[right])) {
                window.add(s[right++])
                ans = Math.max(ans, right - left)
            } else {
                // slide left pointer
                window.remove(s[left++])
            }
        }

        return ans
    }

}