187. Repeated DNA Sequences

最新推荐文章于 2024-08-17 16:52:22 发布

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最新推荐文章于 2024-08-17 16:52:22 发布

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本文介绍了一种使用哈希函数快速定位DNA分子中长度为10的重复序列的方法，并通过一个具体的示例展示了如何实现这一算法。

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All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to identify repeated sequences within the DNA.

Write a function to find all the 10-letter-long sequences (substrings) that occur more than once in a DNA molecule.

For example,

Given s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT",

Return:
["AAAAACCCCC", "CCCCCAAAAA"].

public class Solution {
    public int hashcode(String s){
    	int res = 0;
    	for(int i=0; i<s.length(); i++){
    		res = res << 2 | hash(s.charAt(i));
    	}
    	return res;
    }
    
    public List<String> findRepeatedDnaSequences(String s) {
    	List<String> list = new LinkedList<String>();
        if(s == null || s.length() <= 10){
        	return list;
        }
        HashSet<Integer> set = new HashSet<Integer>();
        for(int i=0; i<=s.length() - 10; i++){
        	String tmp = s.substring(i, i + 10);
        	int hash = hashcode(tmp);
        	if(set.contains(hash) && !list.contains(tmp)){ //记得判断该字符串不在当前的list里面
        		list.add(tmp);
        	}else{
        		set.add(hash);
        	}
        }
        return list;
    }

    public static int hash(char c){
    	if(c == 'A'){
    		return 0;
    	}else if(c == 'C'){
    		return 1;
    	}else if(c == 'G'){
    		return 2;
    	}else if(c == 'T'){
    		return 3;
    	}
		return 0;
    }
}

将字符转换为整数型以便节约空间。