Added one away

Author: rampatra

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

@@ -0,0 +1,67 @@
+package com.ctci.arraysandstrings;
+
+/**
+ * @author rampatra
+ * @since 24/11/2018
+ */
+public class OneAway {
+
+    /**
+     * Checks if two strings are only one edit away, that is, by inserting, deleting, or editing
+     * at max one character in {@code s1} it becomes same as {@code s2}.
+     *
+     * @param s1
+     * @param s2
+     * @return
+     */
+    private static boolean isOneEditAway(String s1, String s2) {
+        if (s1.length() == s2.length()) {
+            return isOneCharacterDiffAtMax(s1, s2);
+        } else if (s1.length() < s2.length()) {
+            return checkForMaxOneInsertOrDeleteInS1(s1, s2);
+        } else {
+            return checkForMaxOneInsertOrDeleteInS1(s1, s2);
+        }
+    }
+
+    private static boolean isOneCharacterDiffAtMax(String s1, String s2) {
+        boolean foundDiff = false;
+        for (int i = 0; i < s1.length(); i++) {
+            if (s1.charAt(i) != s2.charAt(i)) {
+                if (foundDiff) {
+                    return false; // means we already found a difference earlier
+                }
+                foundDiff = true;
+            }
+        }
+        return true;
+    }
+
+    private static boolean checkForMaxOneInsertOrDeleteInS1(String s1, String s2) {
+        int i = 0;
+        int j = 0;
+        int s1Len = s1.length();
+        int s2Len = s2.length();
+        while (i < s1Len && j < s2Len) {
+            if (s1.charAt(i) != s2.charAt(j)) {
+                if (s1Len > s2Len) {
+                    i++;
+                } else {
+                    j++;
+                }
+                continue;
+            }
+            i++;
+            j++;
+        }
+        return Math.abs(i - j) <= 1; // check whether difference in two strings is not more than 1
+    }
+
+    public static void main(String[] args) {
+        System.out.println("pale,  ple: " + isOneEditAway("pale", "ple"));
+        System.out.println("pales,pale: " + isOneEditAway("pales", "pale"));
+        System.out.println("pale, bale: " + isOneEditAway("pale", "bale"));
+        System.out.println("pale, bake: " + isOneEditAway("pale", "bake"));
+        System.out.println("ram, rama: " + isOneEditAway("ram", "rama"));
+    }
+}