78. Longest Common Prefix【medium】

Given k strings, find the longest common prefix (LCP).

 

Example

For strings "ABCD", "ABEF" and "ACEF", the LCP is "A"

For strings "ABCDEFG", "ABCEFG" and "ABCEFA", the LCP is "ABC"

解法一：

 class Solution {
 public:
     /**
      * @param strs: A list of strings
      * @return: The longest common prefix
      */
     int min(int a, int b) {
         return ((a < b) ? a : b);
     }

     int calCount(string & a, string & b) {
         int la = a.size();
         int lb = b.size();
         int count = ;

         for (int i = ; i < la && i < lb; ++i) {
             if (a[i] == b[i]) {
                 count++;
             } else {
                 return count;
             }
         }
     }

     string longestCommonPrefix(vector<string> &strs) {
         int count = INT_MAX;
         int size = strs.size();

         if (size == ) {
             return "";
         }

         for (int i = ; i < strs.size() - ; ++i) {
             count = min(calCount(strs[i], strs[i + ]), count);
         }

         return strs[].substr(, count);
     }
 };

解法二：

 class Solution {
 public:
     /**
      * @param strs: A list of strings
      * @return: The longest common prefix
      */
     string longestCommonPrefix(vector<string> &strs) {
         if (strs.size() == ) {
             return "";
         }

         string prefix = "";
         for (int i = ; i < strs[].length(); i++) {
             for (int j = ; j < strs.size(); j++) {
                 if (strs[j][i] != strs[][i]) {
                     return prefix;
                 }
             }
             prefix += strs[][i];
         }

         return prefix;
     }
 };