Longest Substring Without Repeating Characters
Total Accepted: 152787 Total
Submissions: 687012 Difficulty: Medium
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.
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(H) Longest Substring with At Most Two Distinct Characters
思路：
保护1个HashMap存储每一个字符的位置；两个指针i,j，保护最长子串的范围。
java code:
public class Solution {
public int lengthOfLongestSubstring(String s) {
if(s==null || s.length()==0) return 0;
Map<Character, Integer> map = new HashMap<Character, Integer>();
int max = 0;
for(int i=0,j=0;i<s.length();i++) {
char c = s.charAt(i);
if(map.containsKey(c)) {
j = Math.max(j, map.get(c)+1);
}
map.put(c, i);
max = Math.max(max, i-j+1);
}
return max;
}
}