Create validSentence.js

validSentence.js

@@ -0,0 +1,71 @@
+/* TODO: fill in the task
+
+time complexity: O(n)
+space complexity: 
+*/
+
+
+/* helper functions */
+function isLetter(char) {
+  // Check if the character is a letter by checking its Unicode value
+  const charCode = char.charCodeAt(0);
+  return (
+    (charCode >= 65 && charCode <= 90) || // Uppercase letters A-Z
+    (charCode >= 97 && charCode <= 122)
+  ); // Lowercase letters a-z
+}
+
+function isUpperCaseLetter(char) {
+  // Check if the character is an uppercase letter by checking its Unicode value
+  const charCode = char.charCodeAt(0);
+  return charCode >= 65 && charCode <= 90;
+}
+
+function validSentence(string) {
+  let previousChar = null;
+
+  for (let i = 0; i < string.length; i++) {
+    const currentChar = string[i];
+
+    // if previous char is null
+    // we must have a letter now (any case)
+    if (previousChar === null) {
+      if (!isLetter(currentChar)) {
+        return false;
+      } else {
+        previousChar = currentChar;
+      }
+    // if it is not null, it is a middle of a word
+    } else {
+      // end previous word if it is space
+      if (currentChar === " ") {
+        previousChar = null;
+      // upper case letters are not allowed in the middle of the word
+      } else if (isUpperCaseLetter(currentChar)) {
+        return false;
+      // if it is not a letter, it is not a valid sentence
+      } else if (!isLetter(currentChar)) {
+        return false;
+      } else {
+        previousChar = currentChar;
+      }
+    }
+  }
+
+  // if you get to the end and currentChar is null
+  // the string was either empty, or ended on a space
+  if (previousChar === null) {
+    return false;
+  }
+
+  // we exhausted all cases when it is not valid sentence
+  return true;
+}
+
+console.log(validSentence(" A d  dh") === false);
+console.log(validSentence("A d dh ") === false);
+console.log(validSentence("A d dh") === true);
+console.log(validSentence("A d  dh") === false);
+console.log(validSentence("A d  Adh ") === false);
+console.log(validSentence("A d dSh") === false);
+console.log(validSentence(" A Addh") === false);