算法分析与设计——LeetCode Problem.3 Longest Substring Without Repeating Characters

题目链接

问题描述

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.

解题思路

比较容易想到的办法是把每个字符遍历一遍，到达一个字符时就向前回溯，添加一个变量repeat记录回溯时遇到相同字符的位置，在下一个字符的回溯时如果也遇到了

相同的字符，则将其位置与repeat对比，若其位置靠后则令其为repeat，如此则可以避免在回溯时回溯的字串中包含相同字符的情况

class Solution {public:    int lengthOfLongestSubstring(string s) {    int totalLength = s.size();    if (totalLength == 0) {return 0;}if (totalLength == 1) {return 1;}int p = 0;int backtrack = 0;int maxLength = 0;int subLength = 0;int repeat = -1;for (p = 0; p < totalLength; p++) {for (backtrack = p - 1; backtrack >= 0; backtrack--) {if (s[backtrack] == s[p]) {if (repeat < backtrack) {repeat = backtrack;}break;}}subLength = p - repeat;if (maxLength < subLength) {maxLength = subLength;}}if (maxLength == 0) {return totalLength;}if (maxLength < subLength) {maxLength = subLength;}return maxLength;}};