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.

Note:

All given inputs are in lowercase letters a-z.

Solution:

注意向量为空的情况

class Solution {
 public:
  string longestCommonPrefix(vector<string> &strs) {
    string res = "";

    for (int i = 0; strs.size() > 0; i++) {
      for (int j = 0; j < strs.size(); j++) {
        if ((i >= strs[j].size()) ||  (j > 0 && strs[j][i] != strs[j-1][i])) {
          return res;
        }
      }
      res += strs[0][i];
    }
    return res;
  }

};