78. Longest Common Prefixmedium

Posted 2020-10-23 abc_begin

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：

 1 class Solution {
 2 public:    
 3     /**
 4      * @param strs: A list of strings
 5      * @return: The longest common prefix
 6      */
 7     int min(int a, int b) {
 8         return ((a < b) ? a : b);
 9     }
10      
11     int calCount(string & a, string & b) {
12         int la = a.size();
13         int lb = b.size();
14         int count = 0;
15         
16         for (int i = 0; i < la && i < lb; ++i) {
17             if (a[i] == b[i]) {
18                 count++;
19             } else {
20                 return count;
21             }
22         }
23     }
24      
25     string longestCommonPrefix(vector<string> &strs) {
26         int count = INT_MAX;
27         int size = strs.size();
28         
29         if (size == 0) {
30             return "";
31         }
32         
33         for (int i = 0; i < strs.size() - 1; ++i) {
34             count = min(calCount(strs[i], strs[i + 1]), count);
35         }
36         
37         return strs[0].substr(0, count);
38     }
39 };

 

解法二：

 1 class Solution {
 2 public:    
 3     /**
 4      * @param strs: A list of strings
 5      * @return: The longest common prefix
 6      */
 7     string longestCommonPrefix(vector<string> &strs) {
 8         if (strs.size() == 0) {
 9             return "";
10         }
11         
12         string prefix = "";
13         for (int i = 0; i < strs[0].length(); i++) {
14             for (int j = 1; j < strs.size(); j++) {
15                 if (strs[j][i] != strs[0][i]) {
16                     return prefix;
17                 }
18             }
19             prefix += strs[0][i];
20         }
21         
22         return prefix;
23     }
24 };