All the Test Cases were Passed - Jiutian Yu

StringArrayUtils.java

@@ -1,4 +1,8 @@
-
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
 
 /**
  * Created by Yang on 1/23/20.
@@ -9,31 +13,31 @@ public class StringArrayUtils {
      * @return first element of specified array
      */ // TODO
     public static String getFirstElement(String[] array) {
-        return null;
+        return (array == null || array.length == 0) ? null : array[0];
     }
 
     /**
      * @param array array of String objects
      * @return second element in specified array
      */
     public static String getSecondElement(String[] array) {
-        return null;
+        return (array == null || array.length == 0) ? null : array[1];
     }
 
     /**
      * @param array array of String objects
      * @return last element in specified array
      */ // TODO
     public static String getLastElement(String[] array) {
-        return null;
+        return (array == null || array.length == 0) ? null : array[array.length - 1];
     }
 
     /**
      * @param array array of String objects
      * @return second to last element in specified array
      */ // TODO
     public static String getSecondToLastElement(String[] array) {
-        return null;
+        return (array == null || array.length == 0) ? null : array[array.length - 2];
     }
 
     /**
@@ -42,6 +46,8 @@ public static String getSecondToLastElement(String[] array) {
      * @return true if the array contains the specified `value`
      */ // TODO
     public static boolean contains(String[] array, String value) {
+        if (array == null || array.length == 0) return false;
+        for (String s : array) if (s.equals(value)) return true;
         return false;
     }
 
@@ -50,23 +56,43 @@ public static boolean contains(String[] array, String value) {
      * @return an array with identical contents in reverse order
      */ // TODO
     public static String[] reverse(String[] array) {
-        return null;
+        if (array == null || array.length < 2) return array;
+        int i = 0, j = array.length - 1;
+        while (i < j) {
+            String tmp = array[i];
+            array[i++] = array[j];
+            array[j--] = tmp;
+        }
+        return array;
     }
 
     /**
      * @param array array of String objects
      * @return true if the order of the array is the same backwards and forwards
      */ // TODO
     public static boolean isPalindromic(String[] array) {
-        return false;
+        if (array == null || array.length == 0) return false;
+        int i = 0, j = array.length - 1;
+        while (i < j) if (!array[i++].equals(array[j--])) return false;
+        return true;
     }
 
     /**
      * @param array array of String objects
      * @return true if each letter in the alphabet has been used in the array
      */ // TODO
     public static boolean isPangramic(String[] array) {
-        return false;
+        if (array == null || array.length == 0) return false;
+        Set<Character> set = new HashSet<>();
+        for (char c = 'a'; c <= 'z'; c++) {
+            set.add(c);
+        }
+        for (String s : array) {
+            for (char c : s.toCharArray()) {
+                set.remove(Character.toLowerCase(c));
+            }
+        }
+        return set.isEmpty();
     }
 
     /**
@@ -75,7 +101,10 @@ public static boolean isPangramic(String[] array) {
      * @return number of occurrences the specified `value` has occurred
      */ // TODO
     public static int getNumberOfOccurrences(String[] array, String value) {
-        return 0;
+        if (array == null || array.length == 0) return 0;
+        int result = 0;
+        for (String s : array) if (s.equals(value)) result++;
+        return result;
     }
 
     /**
@@ -84,23 +113,43 @@ public static int getNumberOfOccurrences(String[] array, String value) {
      * @return array with identical contents excluding values of `value`
      */ // TODO
     public static String[] removeValue(String[] array, String valueToRemove) {
-        return null;
+        return Arrays.stream(array).filter(e -> !e.equals(valueToRemove)).toArray(String[] :: new);
     }
 
     /**
      * @param array array of chars
      * @return array of Strings with consecutive duplicates removes
      */ // TODO
     public static String[] removeConsecutiveDuplicates(String[] array) {
-        return null;
+        if (array == null || array.length < 2) return array;
+        int i = 1;
+        for (int j = 1; j < array.length; j++) {
+            if (array[j] != array[i - 1]) {
+                array[i++] = array[j];
+            }
+        }
+        String[] result = new String[i];
+        for (int j = 0; j < i; j++) result[j] = array[j];
+        return result;
     }
 
     /**
      * @param array array of chars
      * @return array of Strings with each consecutive duplicate occurrence concatenated as a single string in an array of Strings
      */ // TODO
     public static String[] packConsecutiveDuplicates(String[] array) {
-        return null;
+        if (array == null || array.length < 2) return array;
+        List<String> result = new ArrayList<>();
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < array.length; i++) {
+            if (i != 0 && !array[i].equals(array[i - 1])) {
+                result.add(sb.toString());
+                sb.delete(0, sb.length());
+            }
+            sb.append(array[i]);
+        }
+        result.add(sb.toString());
+        return result.toArray(new String[0]);
     }