Adding 678-Valid-Parenthesis-String.c

Author: FahadulShadhin

c/678-Valid-Parenthesis-String.c

@@ -0,0 +1,35 @@
+/*
+    Time: O(n)
+    Space: O(1)
+*/
+
+bool checkValidString(char * s) {
+    int n = strlen(s);
+    
+    int balanced = 0;
+    for (int i=0; i<n; i++) {
+        if (s[i] == '(' || s[i] == '*') 
+            balanced++;
+        else 
+            balanced--;
+        
+        if (balanced < 0) 
+            return false;
+    }
+    
+    if (balanced == 0) 
+        return true;
+
+    balanced = 0;
+    for (int i=n-1; i>=0; i--) {
+        if (s[i] == ')' || s[i] == '*') 
+            balanced++;
+        else 
+            balanced--;
+        
+        if (balanced < 0) 
+            return false;
+    }
+    
+    return true;
+}