Added _394.java (fishercoder1534#31)

varunu28 · fishercoder1534 · commit d35b3b74cfa8 · 2019-01-10T19:32:45.000-08:00
Added _394.java
diff --git a/README.md b/README.md
@@ -371,6 +371,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |397|[Integer Replacement](https://leetcode.com/problems/integer-replacement/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_397.java)| ? | ? | |Easy| BFS
 |396|[Rotate Function](https://leetcode.com/problems/rotate-function/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_396.java)| O(n^2) could be optimized to O(n) | O(1) | |Easy|
 |395|[Longest Substring with At Least K Repeating Characters](https://leetcode.com/problems/longest-substring-with-at-least-k-repeating-characters/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_395.java)| O(n^2) | O(1) | |Medium| Recursion
+|394|[Decode String](https://leetcode.com/problems/decode-string/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_394.java)| O(n) | O(n) | |Medium| Stack Depth-first-search
 |393|[UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_393.java)| O(?)|O(?) | |Medium| Bit Manipulation
 |392|[Is Subsequence](https://leetcode.com/problems/is-subsequence/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_392.java)| O(m*n)|O(1) | |Medium| Array, String
 |391|[Perfect Rectangle](https://leetcode.com/problems/perfect-rectangle/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_391.java)| O(n)|O(1) | |Hard| 
diff --git a/src/main/java/com/fishercoder/solutions/_394.java b/src/main/java/com/fishercoder/solutions/_394.java
@@ -0,0 +1,45 @@
+package com.fishercoder.solutions;
+
+import java.util.Stack;
+
+public class _394 {
+
+    public static class Solution1 {
+        public String decodeString(String s) {
+            Stack<Integer> count = new Stack<>();
+            Stack<String> str = new Stack<>();
+
+            int idx = 0;
+            str.push("");
+
+            while(idx < s.length()) {
+                if (s.charAt(idx) >= '0' && s.charAt(idx) <= '9') {
+                    int start = idx;
+                    while (s.charAt(idx + 1) >= '0' && s.charAt(idx + 1) <= '9') {
+                        idx++;
+                    }
+
+                    count.push(Integer.parseInt(s.substring(start, idx + 1)));
+                } else if (s.charAt(idx) == '[') {
+                    str.push("");
+                } else if (s.charAt(idx) == ']') {
+                    String st = str.pop();
+                    StringBuilder sb = new StringBuilder();
+                    int n = count.pop();
+
+                    for (int j = 0; j < n; j++) {
+                        sb.append(st);
+                    }
+
+                    str.push(str.pop() + sb.toString());
+                } else {
+                    str.push(str.pop() + s.charAt(idx));
+                }
+
+                idx++;
+            }
+
+            return str.pop();
+        }
+    }
+}
diff --git a/src/test/java/com/fishercoder/_394Test.java b/src/test/java/com/fishercoder/_394Test.java
@@ -0,0 +1,33 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._394;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Created by varunu28 on 1/08/19.
+ */
+
+public class _394Test {
+    private static _394.Solution1 test;
+
+    public static void setUp() {
+        test = new _394.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals("aaabcbc", test.decodeString("3[a]2[bc]"));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals("accaccacc", test.decodeString("3[a2[c]]"));
+    }
+
+    @Test
+    public void test3() {
+        assertEquals("abcabccdcdcdef", test.decodeString("2[abc]3[cd]ef"));
+    }
+}
