Day 14 - String II

.gitignore

@@ -1 +1,3 @@
 .vscode/
+
+*.class

StringII.java

@@ -3,7 +3,8 @@
 public class StringII {
     public static void main(String[] args) {
         StringII s = new StringII();
-        System.out.println(s.rightShift("abcdefg", 39));
+        // System.out.println(s.rightShift("abcdefg", 39));
+        System.out.println(s.replace("123", "12", "4"));
     }
 
     /**
@@ -69,6 +70,54 @@ public String rightShift(String input, int n) {
         return new String(ch, n, ch.length - n) + new String(ch, 0, n);
     }
 
+    /**
+     * String Replace (basic)
+     * <p>
+     * Given an original string input, and two strings S and T, from left to right
+     * replace all occurrences of S in input with T.
+     */
+    public String replace(String input, String source, String target) {
+        char[] array = input.toCharArray();
+        if (source.length() > input.length()) {
+            return input;
+        }
+        if (target.length() > source.length()) {
+            return replaceLonger(array, source, target);
+        } else {
+            return replaceShorter(array, source, target);
+        }
+    }
+
+    private String replaceShorter(char[] array, String source, String target) {
+        int i = 0;
+        int j = 0;
+        while (i < array.length) {
+            if (isSubString(array, i, source)) {
+                i += source.length();
+                for (int k = 0; k < target.length(); k++) {
+                    array[j++] = target.charAt(k);
+                }
+            } else {
+                array[j++] = array[i++];
+            }
+        }
+        return new String(array, 0, j);
+    }
+
+    private String replaceLonger(char[] array, String source, String target) {
+        StringBuilder sb = new StringBuilder();
+        int i = 0;
+        while (i < array.length) {
+            if (isSubString(array, i, source)) {
+                i += source.length();
+                sb.append(target);
+            } else {
+                sb.append(array[i++]);
+            }
+        }
+        return sb.toString();
+    }
+
     /**
      * All Permutations II
      * <p>
@@ -77,7 +126,130 @@ public String rightShift(String input, int n) {
      */
     public List<String> permutations(String input) {
         List<String> result = new ArrayList<>();
+    }
+
+
+    private boolean isSubString(char[] array, int start, String source) {
+        if (start + source.length() > array.length) {
+            return false;
+        }
 
+        for (int i = 0; i < source.length(); i++) {
+            if (array[i + start] != source.charAt(i)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * ReOrder Array
+     * <p>
+     * Given an array of elements, reorder it as follow: * { N1, N2, N3, …, N2k } ->
+     * { N1, Nk+1, N2, Nk+2, N3, Nk+3, … , Nk, N2k } * { N1, N2, N3, …, N2k+1 } -> {
+     * N1, Nk+1, N2, Nk+2, N3, Nk+3, … , Nk, N2k, N2k+1 } Try to do it in place
+     */
+    public int[] reorder(int[] array) {
+        int[] result = new int[array.length];
+        for (int i = 0; i < array.length / 2; i++) {
+            result[2 * i] = array[i];
+            result[2 * i + 1] = array[i + array.length / 2];
+        }
+        if (array.length % 2 == 1) {
+            result[array.length - 1] = array[array.length - 1];
+        }
         return result;
     }
+
+    /**
+     * Compress String II
+     * <p>
+     * Given a string, replace adjacent, repeated characters with the character
+     * followed by the number of repeated occurrences.
+     */
+    public String compress(String input) {
+        char prev = (char) 0;
+        StringBuilder sb = new StringBuilder();
+        int cur = 0;
+        for (char c : input.toCharArray()) {
+            if (cur == 0) {
+                prev = c;
+                cur = 1;
+                continue;
+            }
+            if (prev == c) {
+                cur++;
+            } else {
+                sb.append(prev);
+                sb.append(cur);
+                cur = 1;
+                prev = c;
+            }
+        }
+        if (cur != 0) {
+            sb.append(prev);
+            sb.append(cur);
+        }
+        return sb.toString();
+    }
+
+    /**
+     * Decompress String II
+     * <p>
+     * Given a string in compressed form, decompress it to the original string. The
+     * adjacent repeated characters in the original string are compressed to have
+     * the character followed by the number of repeated occurrences.
+     */
+    public String decompress(String input) {
+        char[] array = input.toCharArray();
+        int l = 0;
+        StringBuilder sb = new StringBuilder();
+        char prev = (char) 0;
+
+        for (char c : array) {
+            if (c - '0' < 10 && c - '0' >= 0) {
+                l *= 10;
+                l += c - '0';
+            } else {
+                while (l-- > 0) {
+                    sb.append(prev);
+                }
+                l = 0;
+                prev = c;
+            }
+        }
+        while (l-- > 0) {
+            sb.append(prev);
+        }
+        return sb.toString();
+    }
+
+    /**
+     * Longest Substring Without Repeating Characters
+     * <p>
+     * Given a string, find the longest substring without any repeating characters
+     * and return the length of it. The input string is guaranteed to be not null.
+     * For example, the longest substring without repeating letters for "bcdfbd" is
+     * "bcdf", we should return 4 in this case.
+     */
+    public int longest(String input) {
+        int max = 0;
+        boolean[] set = new boolean[26];
+        int i = 0;
+        int j = 0;
+        while (j < input.length()) {
+            if (!set[input.charAt(j) - 'a']) {
+                set[input.charAt(j++) - 'a'] = true;
+                max = Math.max(max, j - i);
+            } else {
+                while (input.charAt(i) != input.charAt(j)) {
+                    set[input.charAt(i++) - 'a'] = false;
+                }
+                set[input.charAt(i++) - 'a'] = false;
+                set[input.charAt(j++) - 'a'] = true;
+            }
+        }
+        return max;
+    }
+
 }