Added urlify

Author: rampatra

src/main/java/com/ctci/arraysandstrings/CheckPermutation.java

@@ -8,6 +8,13 @@
  */
 public class CheckPermutation {
 
+    /**
+     * Checks if {@code s1} is a permutation of {@code s2}.
+     *
+     * @param s1
+     * @param s2
+     * @return
+     */
     private static boolean isOnePermutationOfOther(String s1, String s2) {
         if (s1.length() != s2.length()) {
             return false;
@@ -21,6 +28,13 @@ private static boolean isOnePermutationOfOther(String s1, String s2) {
         return Arrays.equals(c1, c2);
     }
 
+    /**
+     * Checks if {@code s1} is a permutation of {@code s2}.
+     *
+     * @param s1
+     * @param s2
+     * @return
+     */
     private static boolean isOnePermutationOfOtherGivenThatStringsContainOnlyAscii(String s1, String s2) {
         if (s1.length() != s2.length()) {
             return false;

src/main/java/com/ctci/arraysandstrings/URLify.java

@@ -0,0 +1,43 @@
+package com.ctci.arraysandstrings;
+
+/**
+ * @author rampatra
+ * @since 19/11/2018
+ */
+public class URLify {
+
+    /**
+     * We space encode the string such that all spaces in the string are replaced with '%20'. The string {@code str}
+     * contains extra spaces to accommodate the extra characters.
+     *
+     * @param str string with spaces
+     * @return string with spaces replaced with %20
+     */
+    private static String urlify(String str) {
+        char[] chars = str.toCharArray();
+        int curr = chars.length - 1; // we will start backwards so that we don't have to worry about characters we overwrite
+        int insertIndex = curr;
+
+        // move the curr pointer to the last character which isn't a space
+        while (chars[curr] == 32) {
+            curr--;
+        }
+
+        while (curr >= 0) {
+            if (chars[curr] == 32) {
+                chars[insertIndex--] = '0';
+                chars[insertIndex--] = '2';
+                chars[insertIndex--] = '%';
+            } else {
+                chars[insertIndex--] = chars[curr];
+            }
+            curr--;
+        }
+        return String.valueOf(chars);
+    }
+
+    public static void main(String[] args) {
+        System.out.println(urlify("Mr John Smith    "));
+        System.out.println(urlify("Mr  Ram Patra      "));
+    }
+}