add problem 3 and test function

Author: supercoderhawk

C/1-50/3-Longest-Substring-Without-Repeating-Characters.c

@@ -0,0 +1,42 @@
+/*
+ * Given a string, find the length of the longest substring without repeating characters.
+ *
+ * Examples:
+ *  Given "abcabcbb", the answer is "abc", which the length is 3.
+ *  Given "bbbbb", the answer is "b", with the length of 1.
+ *  Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.
+ *  Created by supercoderhawk on 2017/7/23.
+ */
+#include 
+#include "../main.h"
+
+
+int lengthOfLongestSubstring(char* s) {
+    int start =0, end = 0,digit = 0, maxLength = 0;
+    char* p = s;
+    int letters[128];
+    for(int i = 0; i < 128; i++)
+        letters[i] = 0;
+
+    while(*p != '\0')
+    {
+        digit = (int)*p;
+        while(letters[digit] != 0)
+        {
+            letters[(int)s[start]] = 0;
+            start += 1;
+        }
+        letters[digit] = 1;
+        end += 1;
+        if (end - start > maxLength)
+            maxLength = end-start;
+        p = p + 1;
+    }
+    return maxLength;
+}
+
+void testLengthOfLongestSubstring()
+{
+    char *p="pwwkew";
+    printf("%d",lengthOfLongestSubstring(p));
+}