【LeetCode】3. Longest Substring Without Repeating Characters

題目：

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

Examples:

Given?"abcabcbb", the answer is?"abc", which the length is 3.

Given?"bbbbb", the answer is?"b", with the length of 1.

Given?"pwwkew", 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.

思路大概是建立一個映射表，遍歷整個字符串，如果字符對應映射表的index值為-1，說明字符沒出現過，計算長度大小，更新maxLength。如果字符出現過，那么就重新開始計算。遍歷后得到最后結果。

class Solution {
public:int lengthOfLongestSubstring(string s) {int indexOfChar[256];memset(indexOfChar, -1, sizeof(indexOfChar));int maxLength = 0;int initIndex = -1;for (int i = 0; i < s.length(); ++i){if (indexOfChar[s[i]] > initIndex){initIndex = indexOfChar[s[i]];}indexOfChar[s[i]]=i;maxLength=max(maxLength, i - initIndex);}return maxLength;}
};

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