算法初体验-3

最新推荐文章于 2024-06-05 08:30:00 发布

原创最新推荐文章于 2024-06-05 08:30:00 发布 · 342 阅读

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早想做一下字符串的题，这个字符串题，自己感觉很经典，同样也是用了哈希表，把通常的O(n2),O(n3)变成了O(n)

Longest Substring Without Repeating Characters

Total Accepted: 52607 Total Submissions: 245781 My Submissions

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.

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java 代码实现

public class Longest_Substring_Without_Repeating_Characters {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
	int a	=lengthOfLongestSubstring("adbcded");
	System.out.println(a);
	}
	 public static int lengthOfLongestSubstring(String s) 
	 { char[] arr = s.toCharArray();
	 int max=0;
		int begin=0;
		int end=0;
		HashSet<Character> characters=new HashSet<Character>();
		while(end<arr.length)
		{
			if(characters.contains(arr[end]))
			{
				while(begin<end&&arr[begin]!=arr[end])
				{
					characters.remove(arr[begin]);
					begin++;
				}
				begin++;end++;
			}
			else
			{
				characters.add(arr[end]);
				end++;
			}
			 max = Math.max(max,end-begin);
		}
		return max;
	 }
}