【算法】Longest Substring Without Repeating Characters 最长无重复字符子串

题目

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.
Example 2:

Input: "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.
Example 3:

Input: "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

给出一个字符串，求出最长的无重复字符的子串的长度。

解题思路

滑动窗口：

1. 移动窗口的右边界 right ，
2. 在 map 中寻找 right所指字符 chare
   • 找到则说明为重复字符，取 map[chare] + 1 和 left 较大值，更新窗口左边界 left
   • 没找到则将 chare 和索引 right 加入到 map 中
3. 取 right - left + 1 和 res 较大值，更新结果 res

代码实现

Runtime: 36 ms
Memory: 21.6 MB

func lengthOfLongestSubstring(_ s: String) -> Int {
        //字符串长度小于 2 时，直接返回字符串长度
        let sCount = s.count
        if(sCount < 2){
            return sCount
        }
        var res = 0,left = 0
        var sArr = Array(s)
        var map = [Character:Int]()
        //遍历字符串
        for right in 0 ..< sCount{
            //获取 right 所指字符 chare
            let chare = sArr[right]
            //若 map 中含有 chare，则更新 left
            if let rIdx = map[chare] {
                left = max(left, rIdx + 1)
            }
            //将 chare 和 right 加入到 map 中
            map[chare] = right
            //更新 res
            res = max(right - left + 1, res)
        }
        return res
    }

代码地址：https://github.com/sinianshou/EGSwiftLearning