add leetcode/cpp/string/14.cpp file with the solution for the 14th leetcode task

leetcode/cpp/string/14.cpp

@@ -0,0 +1,38 @@
+/**
+ * 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: str = [ "flower", "flow", "flight" ]
+ * output: "fl"
+ *
+ *
+ @author of the code is vi (yeah that's the nickname
+ */
+
+class Solution {
+    constexpr static size_t THE_PREFIX_START_{0};
+
+public:
+    constexpr inline std::string longestCommonPrefix(const std::vector<std::string>& strs) noexcept {
+        std::string common_prefix{strs[0]};
+
+        // iterating through every string in strs
+        // e stands for element
+        for(const auto& e : strs) {
+            // if we didn't find the prefix, we'll change the prefix until we found it
+            while(e.find(common_prefix) != THE_PREFIX_START_) {
+                common_prefix = common_prefix.substr(0, common_prefix.size()-1);
+                // if common_prefix is an empty string, than it's over
+                if(common_prefix.empty()) {
+                    return "";
+                }
+            }
+        }
+
+        return common_prefix;
+    }
+};