3.Longest Substring Without Repeating Characters（7.66%）

题目：Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for “abcabcbb” is “abc”, which the length is 3. For “bbbbb” the longest substring is “b”, with the length of 1.

个人理解：求最长的没有重复的字符串的长度。刚开始的时候贪图便利，用Java自带的字符串方法进行操作，结果超时了：

public class Solution {
public int lengthOfLongestSubstring(String s) {
int inputLength = s.length();

int longestLength = 0;
for (int i = 0; i < inputLength; i++) {
String tempString = String.valueOf(s.charAt(i));

for (int j = i + 1; j < inputLength; j++) {
String character = String.valueOf(s.charAt(j));
if (tempString.contains(character)) {
break;
} else {
tempString = tempString.concat(character);
}
}
longestLength = longestLength > tempString.length() ? longestLength : tempString.length();
}

return longestLength;
}
}

后来百度了一下，才想起Java字符数组：

public class Solution {
public int lengthOfLongestSubstring(String s) {
int inputLength = s.length();
char[] chars = s.toCharArray();

int longestLength = 0;
for (int i = 0; i < inputLength; i++) {
int oneLength = 0;
for (int j = i + 1; j < inputLength; j++) {

boolean isLegal = true;
for (int k = i; k < j; k++) {
if (chars[k] == chars[j]) {
isLegal = false;
break;
}
}

if (isLegal) {
oneLength++;
} else {
break;
}
}

oneLength++;
longestLength = longestLength > oneLength ? longestLength : oneLength;

if (longestLength == inputLength) {
return longestLength;
}
}
return longestLength;
}
}