Add Longest Palindromic Substring in C++ (TheRenegadeCoder#5096)

Author: MeetThakur

archive/c/c-plus-plus/longest-palindromic-substring.cpp

@@ -0,0 +1,60 @@
+#include <iostream>
+#include <string>
+#include <cstring>
+
+#define MAX_LENGTH 1000
+
+int expandAroundCenter(const std::string& s, int left, int right) {
+    while (left >= 0 && right < s.length() && s[left] == s[right]) {
+        left--;
+        right++;
+    }
+    return right - left - 1;
+}
+
+bool longestPalindromicSubstring(const std::string& s, std::string& result) {
+    if (s.empty()) {
+        result = "";
+        return false;
+    }
+
+    int start = 0, maxLength = 0;
+    int len = s.length();
+
+    for (int i = 0; i < len; i++) {
+        int len1 = expandAroundCenter(s, i, i);
+        int len2 = expandAroundCenter(s, i, i + 1);
+        int len = (len1 > len2) ? len1 : len2;
+
+        if (len > maxLength) {
+            start = i - (len - 1) / 2;
+            maxLength = len;
+        }
+    }
+
+    if (maxLength > 1) {
+        result = s.substr(start, maxLength);
+        return true;
+    }
+
+    result = "";
+    return false;
+}
+
+int main(int argc, char* argv[]) {
+    if (argc != 2) {
+        std::cout << "Usage: please provide a string that contains at least one palindrome" << std::endl;
+        return 1;
+    }
+
+    std::string input = argv[1];
+    std::string result;
+
+    if (longestPalindromicSubstring(input, result) && !result.empty()) {
+        std::cout << result << std::endl;
+    } else {
+        std::cout << "Usage: please provide a string that contains at least one palindrome" << std::endl;
+    }
+
+    return 0;
+}