Leetcode优化：Longest Common Prefix

最新推荐文章于 2021-05-03 09:07:26 发布

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最新推荐文章于 2021-05-03 09:07:26 发布

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本文链接：https://blog.youkuaiyun.com/hello_qingwen/article/details/37955945

本文介绍了一种寻找字符串列表中最长公共前缀的高效算法，包括直觉方法和使用Trie树的方法，详细分析了两种方法的时间复杂度和空间复杂度。

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Longest Common Prefix

A straight method for this problem is the brute force by enumerating the length of the prefix from 0, and ends until we find the longest common prefix.

class Solution {
public:
    string longestCommonPrefix(vector<string> &strs) {
        int start=0;
        int len=0;
        if(strs.size()==0) return "";
        int minLen=strs[0].length();
        
        for(int i=0; i<strs.size(); i++){  //An important observation to accelerate the process 
            if(minLen>strs[i].length())
                minLen=strs[i].length();
        }
        int i;
        for(i=0; i<minLen; i++){
            for(int j=1; j<strs.size(); j++){
                if(strs[j][i]!=strs[j-1][i]){ //break if the condition is not satisfied
                    len=i-start;
                    return strs[0].substr(start, len);
                }
            }
        }
        len=i-start;
        return strs[0].substr(start, len);
    }
};

This time complexity is O(m*l) where l is the minimum length of the string, and the space complexity is O(1)

Another method for finding the longest common prefix is the trie tree, which results in O(n) in time complexity and O(n) in space, as well.