Merge pull request neetcode-gh#2025 from andrewmustea/c_0392-is-subse…

…quence_use_pointers

c: 0392-is-subsequence: use pointers instead of recursion

c/0392-is-subsequence.c

@@ -1,18 +1,44 @@
-/*
-Given two strings s and t, return true if s is a subsequence of t, or false otherwise.
+/**
+ * Given two strings s and t, return true if s is a subsequence of t, or false
+ * otherwise. A subsequence of a string is a new string that is formed from the
+ * original string by deleting some (can be none) of the characters without
+ * disturbing the relative positions of the remaining characters. (i.e., "ace"
+ * is a subsequence of "abcde" while "aec" is not).
+ *
+ * Example 1:
 
-Space: O(1)
-Time: O(n)
-*/
+ * Input: s = "abc", t = "ahbgdc"
+ * Output: true
+ *
+ * Example 2:
+ *
+ * Input: s = "axc", t = "ahbgdc"
+ * Output: false
+ *
+ * Constraints:
+ *
+ * 0 <= s.length <= 100
+ * 0 <= t.length <= 104
+ * s and t consist only of lowercase English letters.
+ *
+ * Space: O(1)
+ * Time: O(n)
+ */
 
 bool isSubsequence(char * s, char * t){
-    if (s[0]=='\0'){
-        return true;
-    } else if (t[0]=='\0') {
-        return false;
-    } else if (t[0]==s[0]) {
-        return isSubsequence(s+1, t+1);
-    } else {
-        return isSubsequence(s, t+1);
+    char *s_char = s;
+    char *t_char = t;
+
+    while (*s_char != 0) {
+        if (*t_char == 0) {
+            return false;
+        }
+        else if (*s_char == *t_char) {
+            ++s_char;
+        }
+
+        ++t_char;
     }
+
+    return true;
 }