add problem 5 and test function

Author: supercoderhawk

C/1-50/5.-Longest-Palindromic-Substring.c

@@ -0,0 +1,129 @@
+/*
+ * Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.
+ * Example:
+ *  Input: "babad"
+ *  Output: "bab"
+ *  Note: "aba" is also a valid answer.
+ * Created by supercoderhawk on 2017/7/23.
+ */
+
+#include 
+#include 
+#include 
+
+char *longestPalindrome(char *s) {
+    if (s == NULL)
+        return s;
+    int maxLength = 0, maxStart = 0, maxEnd = 0, length = 0, isReverse = 0;
+    int start = -1, end = -1,reverseStart = 0,reverseEnd = 0;
+    char *pStr = s;
+    while (*pStr != '\0') {
+        length++;
+        pStr++;
+    }
+
+    char *reverseStr = (char *) malloc(sizeof(char) * (length + 1));
+    for (int i = 0; i < length; i++) {
+        reverseStr[i] = s[length - 1 - i];
+    }
+    reverseStr[length] = '\0';
+    for (int i = 1; i <= length; i++) {
+        start = end = reverseStart = reverseEnd = -1;
+        for (int j = 0; j < i; j++) {
+            if (start == -1 && s[j] == reverseStr[length - i + j]) {
+                start = j;
+                reverseStart = i - j;
+            } else if (start != -1 && s[j] != reverseStr[length - i + j]) {
+                end = j;
+                reverseEnd =  i - j;
+                if( start == reverseEnd && end == reverseStart)
+                {
+                    if (end - start > maxLength) {
+                        maxLength = end - start;
+                        maxEnd = end;
+                        maxStart = start;
+                    }
+                }
+                start = end = -1;
+            }
+        }
+        if (start != -1 && end == -1)
+        {
+            end = i;
+            reverseEnd = 0;
+            if( start == reverseEnd && end == reverseStart)
+            {
+                if (end - start > maxLength) {
+                    maxLength = end - start;
+                    maxEnd = end;
+                    maxStart = start;
+                }
+            }
+        }
+
+    }
+    for (int i = 1; i <= length; i++) {
+        start = end = -1;
+        for (int j = 0; j < i; j++) {
+            if (start == -1 && s[length - i + j] == reverseStr[j]) {
+                start = j;
+                reverseStart =  i - j;
+            } else if (start != -1 && s[length - i + j] != reverseStr[j]) {
+                end = j;
+                reverseEnd = i - j;
+                if( start == reverseEnd && end == reverseStart)
+                {
+                    if (end - start > maxLength) {
+                        maxLength = end - start;
+                        maxEnd = end;
+                        maxStart = start;
+                        isReverse = 1;
+                    }
+                }
+                start = end = -1;
+            }
+        }
+        if (start != -1 && end == -1)
+        {
+            end = i;
+            reverseEnd = 0;
+            if( start == reverseEnd && end == reverseStart)
+            {
+                if (end - start > maxLength) {
+                    maxLength = end - start;
+                    maxEnd = end;
+                    maxStart = start;
+                    isReverse = 1;
+                }
+            }
+        }
+
+
+    }
+
+    if (maxEnd - maxStart == 0)
+        return '\0';
+    char *palindrome = (char *) malloc(sizeof(char) * (maxEnd - maxStart + 1));
+    if (isReverse)
+        strncpy(palindrome, reverseStr + maxStart, maxEnd - maxStart);
+    else
+        strncpy(palindrome, s + maxStart, maxEnd - maxStart);
+    palindrome[maxEnd - maxStart] = '\0';
+    return palindrome;
+}
+
+void testLongestPalindrome() {
+    char *s1 = "b";
+    printf("%s\n", longestPalindrome(s1));
+    char *s2 = "babad";
+    printf("%s\n", longestPalindrome(s2));
+    char *s3 = "abb";
+    printf("%s\n", longestPalindrome(s3));
+    char *s4 = "abcdasdfghjkldcba";
+    printf("%s\n", longestPalindrome(s4));
+    char *s5 = "cbbd";
+    printf("%s\n", longestPalindrome(s5));
+    char *s6 = "babaddtattarrattatddetartrateedredividerb";
+    printf("%s\n", longestPalindrome(s6));
+}
+