14. Longest Common Prefix
1. Description
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 “”.
2. Example
Example 1
Input: strs = [“flower”,“flow”,“flight”]
Output: “fl”
Example 2
Input: strs = [“dog”,“racecar”,“car”]
Output: ""
Explanation: There is no common prefix among the input strings.
3. Constraints
- 1 <= strs.length <= 200
- 0 <= strs[i].length <= 200
- strs[i] consists of only lowercase English letters if it is non-empty.
4. Solutions
Vertical Scan
m = strs.size(), n = strs[0].size()
Time complexity: O(mn)
Space complexity: O(1)
class Solution {
public:
string longestCommonPrefix(const vector<string> &strs) {
const int min_str_length =
std::min_element(strs.begin(), strs.end(), [](const string &a, const string &b) {
return a.size() < b.size();
})->size();
const int n = strs.size();
for (int i = 0; i < min_str_length; ++i) {
for (int j = 1; j < n; ++j) {
if (strs[j][i] != strs[0][i]) {
return strs[0].substr(0, i);
}
}
}
return strs[0].substr(0, min_str_length);
}
};