14. Longest Common Prefix [LeetCode]

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本文介绍了一种寻找字符串数组中最长公共前缀的方法，并提供了两种实现思路：一种是通过逐字符对比来查找公共前缀，另一种是从首尾两端进行对比缩短匹配范围。这两种方法都可用于快速解决实际应用中的字符串匹配问题。

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14. Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.

If there is no common prefix, return an empty string "".

Example 1:

Input: ["flower","flow","flight"]
Output: "fl"

Example 2:

Input: ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.

//纵向
class Solution_14_1 {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if (strs.empty())return "";

        for (int i = 0; i != strs[0].size(); ++i) {
            for (int j = 0; j != strs.size(); ++j) {
                //第j行的第i个元素 和 第0行的第i个元素比较
                if (strs[j][i] != strs[0][i])
                    return strs[0].substr(0, i);//返回第0行的前i个元素
            }
        }

        return strs[0];
    }
};

//横向
class Solution_14_2 {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if (strs.empty())return "";
        int right = strs[0].size() - 1;
        for (int i = 1; i != strs.size(); ++i) {
            for (int j = 0; j <= right; ++j) {
                if (strs[i][j] != strs[0][j])
                    right = j-1;//下一次比较前j-1个元素，包括j-1
            }
        }
        return strs[0].substr(0, right+1);
    }
};