LeetCode(Array&String)Longest SubString Without Repeating Characters

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.

思路：遇到判断重复的问题，就应该想到set或者map这种结构来辅助提高算法效率。

代码如下：

class Solution {
    public int lengthOfLongestSubstring(String s) {
	        int len=s.length();
	        if(len==0){
	            return 0;
	        }
	        int max=0;
	        if(len==1) {
	        	return 1;
	        }
	       
	        for(int i=0;i<len;i++){
	            Set<Character> set=new HashSet<Character>();
	            char c=s.charAt(i);
	            set.add(c);
	            for(int j=i+1;j<len;j++){
	                char temp=s.charAt(j);
	                if(!set.contains(temp)){
	                    set.add(temp);
	                    if(j==len-1) {
	                    	if(max<len-i) {
	                    		max=len-i;
	                    	}
	                    }
	                }else{
	                    if(max<set.size()){
	                        max=set.size();
	                    }
	                    break;
	                }
	            }
	        }
	        return max;
    }
}