Longest Substring Without Repeating Characters
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.找到最長的子字符串，其思想是一次遍歷，兩個指針i和j，存在map中，如果沒有重複的，則直接+1，如果有重複的，則把j的位置後移，然後計算max
public
int
lengthOfLongestSubstring(String
s)
{if(s.length()==0)return0;
HashMap<Character,
Integer>map=newHashMap<Character, Integer>();
int
max=0;
for(int
i=0,
j=0; i<s.length(); ++i){
if(map.containsKey(s.charAt(i)))
{ j = Math.max(j,map.get(s.charAt(i))+1);
//關鍵點：j只能往後走，不能往前看。
}
map.put(s.charAt(i),i);
max=
Math.max(max,i-j+1);
}
return
max;
}
