Non-repeating character

ardallie · ardallie · commit 8b69a492efa9 · 2021-08-14T13:16:39.000+01:00
diff --git a/src/easy/NonrepeatingCharacter.java b/src/easy/NonrepeatingCharacter.java
@@ -0,0 +1,54 @@
+package easy;
+
+import java.util.HashMap;
+
+/**
+ * Have the function NonrepeatingCharacter(str)
+ * take the str parameter being passed,
+ * which will contain only alphabetic characters and spaces,
+ * and return the first non-repeating character.
+ * ---
+ * For example: if str is "agettkgaeee" then your program should return k.
+ * The string will always contain at least one character and there will
+ * always be at least one non-repeating character.
+ */
+public class NonrepeatingCharacter {
+
+  /**
+   * Non-repeating Character function.
+   *
+   * @param str input string
+   * @return the first non-repeating character
+   */
+  private static String nonrepeatingCharacter(String str) {
+
+    char[] charArr = str.toLowerCase().toCharArray();
+    HashMap<Integer, Integer> freq = new HashMap<>();
+
+    for (int c : charArr) {
+      Integer count = freq.get(c);
+      freq.put(c, count == null ? 1 : ++count);
+    }
+
+    for (int c : charArr) {
+      Integer count = freq.get(c);
+      if (count == 1) {
+        return String.valueOf((char) c);
+      }
+    }
+    return "false";
+  }
+
+  /**
+   * Entry point.
+   *
+   * @param args command line arguments
+   */
+  public static void main(String[] args) {
+    var res1 = nonrepeatingCharacter("Beauty in things exists in the mind which contemplates them");
+    System.out.println(res1);
+    var res2 = nonrepeatingCharacter("A wise man apportions his beliefs to the evidence");
+    System.out.println(res2);
+  }
+
+}
