Longest Common Prefix

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

思路:

先求前两个字符串的公共前缀，然后拿这个前缀和其他字符串进行比对。

 1     int min(int a, int b){
 2         if(a < b)
 3             return a;
 4         return b;
 5     }
 6     string longestCommonPrefix(vector<string> &strs) {
 7         // Note: The Solution object is instantiated only once and is reused by each test case.
 8         int n = strs.size();
 9         if(n == 0)
10             return "";
11         if(n == 1)
12             return strs[0];
13         string s1 = strs[0], s2 = strs[1];
14         int i = 0, j;
15         string result = "";
16         while(s1[i] == s2[i] && i < min(s1.length(), s2.length())){
17             result += s1[i];
18             i++;
19         }
20         for(j = 2; j < n; j++){
21             s1 = strs[j];
22             i = min(s1.length(), i);
23             while(s1[i-1] != result[i-1] && i>0){
24                 i--;
25             }
26         }
27         result = result.substr(0,i);
28         return result;
29     }

 另外一种方法是，依次增加result的长度，判断所有的string在这个位是不是相等。虽然复杂度不变，但是代码变得简练很多。

 1     string longestCommonPrefix(vector<string> &strs) {
 2         int n = strs.size();
 3         if(n == 0)
 4             return "";
 5         if(n == 1)
 6             return strs[0];
 7         int i, j;
 8         string result = "";
 9         for(i = 0;;i++){
10             for(j = 1; j < n; j++){
11                 if(strs[j].length() < i+1 || strs[j][i] != strs[0][i])
12                     break;
13             }
14             if(j < n)
15                 break;
16             result += strs[0][i];
17         }
18         return result;
19     }

 

posted on 2013-10-10 20:29  waruzhi  阅读(172)  评论(0)  编辑  收藏  举报

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