Add new solutions

Author: andrewbayd

src/com/andrewbayd/RansomNote.java

@@ -0,0 +1,34 @@
+package com.andrewbayd;
+
+/*
+Given two strings ransomNote and magazine, return true if ransomNote can be constructed from magazine and false otherwise.
+Each letter in magazine can only be used once in ransomNote.
+
+https://leetcode.com/problems/ransom-note/
+ */
+
+import java.util.HashMap;
+
+public class RansomNote {
+    public boolean canConstruct(String ransomNote, String magazine) {
+        HashMap<Character, Integer> map = new HashMap<>();
+        for (char c : magazine.toCharArray()) {
+            map.put(c, map.getOrDefault(c, 0) + 1);
+        }
+        for (char c : ransomNote.toCharArray()) {
+            if (map.containsKey(c) && map.get(c) > 0) {
+                map.put(c, map.get(c) - 1);
+            } else {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    public static void main(String[] args) {
+        RansomNote note = new RansomNote();
+        System.out.println(note.canConstruct("a", "b")); //-> false
+        System.out.println(note.canConstruct("aa", "ab")); //-> false
+        System.out.println(note.canConstruct("aa", "abba")); //-> true
+    }
+}

src/com/andrewbayd/ReverseInteger.java

@@ -0,0 +1,38 @@
+package com.andrewbayd;
+
+/*
+Given a signed 32-bit integer x, return x with its digits reversed.
+If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.
+Assume the environment does not allow you to store 64-bit integers (signed or unsigned).
+
+https://leetcode.com/problems/reverse-integer/
+ */
+
+public class ReverseInteger {
+    public static int reverse(int x) {
+        if (x == 0) {
+            return 0;
+        }
+
+        int res = 0;
+        while (x != 0) {
+            int last = x % 10;
+            x /= 10;
+            if (res > Integer.MAX_VALUE / 10
+                    || res < Integer.MIN_VALUE / 10
+                    || res == Integer.MAX_VALUE / 10 && last > 7
+                    || res == Integer.MIN_VALUE / 10 && last < -8) {
+                return 0;
+            }
+            res = res * 10 + last;
+        }
+        return res;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(reverse(123)); //-> 321
+        System.out.println(reverse(-321)); //-> -123
+        System.out.println(reverse(1463847412)); //-> 2147483641
+        System.out.println(reverse(1563847412)); //-> 0
+    }
+}