[LeetCode]32. Longest Common Prefix最长公共前缀

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

解法：从所有的string的头到尾的字母逐一比较即可。

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        int n = strs.size(), i = 0;
        bool flag = false;
        if (n == 0) return string("");
        if (n == 1) return strs[0];
        while (true)
        {
            for (int j = 0; j < n - 1; j++)
            {
                if (i >= strs[j].size() || strs[j][i] != strs[j + 1][i])
                {
                    flag = true;
                    break;
                }
            }
            if (flag) break;
            i++;
        }
        return string(strs[0].begin(), strs[0].begin() + i);
    }
};

精简得到一个更简洁的代码版本：

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        int n = strs.size();
        if (n == 0) return string("");
        for(int i = 0; i < strs[0].size(); i++)
        {
            for (int j = 0; j < n - 1; j++)
            {
                if (i >= strs[j].size() || strs[j][i] != strs[j + 1][i])
                    return strs[j].substr(0, i);
            }
        }
        return strs[0];
    }
};