add 546

fishercoder1534 · fishercoder1534 · commit 66a3a398215c · 2017-06-08T23:01:19.000-07:00
diff --git a/README.md b/README.md
@@ -55,6 +55,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |549|[Binary Tree Longest Consecutive Sequence II](https://leetcode.com/problems/binary-tree-longest-consecutive-sequence-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/BinaryTreeLongestConsecutiveSequenceII.java) | O(n) |O(n) | Medium | Tree
 |548|[Split Array with Equal Sum](https://leetcode.com/problems/split-array-with-equal-sum/)|[Solution](../master/src/main/java/com/fishercoder/solutions/SplitArraywithEqualSum.java) | O(n^2) |O(1) | Medium | Array
 |547|[Friend Circles](https://leetcode.com/problems/friend-circles/)|[Solution](../master/src/main/java/com/fishercoder/solutions/FriendCircles.java) | O(n^2) |O(n) | Medium | Union Find
+|546|[Remove Boxes](https://leetcode.com/problems/remove-boxes/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_546.java) | O(n^3) |O(n^3) | Hard| DFS, DP
 |545|[Boundary of Binary Tree](https://leetcode.com/problems/boundary-of-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/BoundaryofBinaryTree.java) | O(n) |O(n) | Medium | Recursion
 |544|[Output Contest Matches](https://leetcode.com/problems/output-contest-matches/)|[Solution](../master/src/main/java/com/fishercoder/solutions/OutputContestMatches.java) | O(n) |O(n) | Medium | Recursion
 |543|[Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/DiameterofBinaryTree.java) | O(n) |O(h) | Easy | Tree/DFS/Recursion
diff --git a/src/main/java/com/fishercoder/solutions/_546.java b/src/main/java/com/fishercoder/solutions/_546.java
@@ -0,0 +1,48 @@
+package com.fishercoder.solutions;
+
+/**
+ * 546. Remove Boxes
+ *
+ * Given several boxes with different colors represented by different positive numbers.
+ You may experience several rounds to remove boxes until there is no box left.
+ Each time you can choose some continuous boxes with the same color (composed of k boxes, k >= 1), remove them and get k*k points.
+ Find the maximum points you can get.
+
+ Example 1:
+ Input:
+
+ [1, 3, 2, 2, 2, 3, 4, 3, 1]
+ Output:
+ 23
+
+ Explanation:
+ [1, 3, 2, 2, 2, 3, 4, 3, 1]
+ ----> [1, 3, 3, 4, 3, 1] (3*3=9 points)
+ ----> [1, 3, 3, 3, 1] (1*1=1 points)
+ ----> [1, 1] (3*3=9 points)
+ ----> [] (2*2=4 points)
+ Note: The number of boxes n would not exceed 100.
+ */
+public class _546 {
+    /**credit: https://leetcode.com/articles/remove-boxes/#approach-2-using-dp-with-memorizationaccepted*/
+    public int removeBoxes(int[] boxes) {
+        int[][][] dp = new int[100][100][100];
+        return calculatePoints(boxes, dp, 0, boxes.length - 1, 0);
+    }
+
+    public int calculatePoints(int[] boxes, int[][][] dp, int l, int r, int k) {
+        if (l > r) return 0;
+        if (dp[l][r][k] != 0) return dp[l][r][k];
+        while (r > l && boxes[r] == boxes[r - 1]) {
+            r--;
+            k++;
+        }
+        dp[l][r][k] = calculatePoints(boxes, dp, l, r - 1, 0) + (k + 1) * (k + 1);
+        for (int i = l; i < r; i++) {
+            if (boxes[i] == boxes[r]) {
+                dp[l][r][k] = Math.max(dp[l][r][k], calculatePoints(boxes, dp, l, i, k + 1) + calculatePoints(boxes, dp, i + 1, r - 1, 0));
+            }
+        }
+        return dp[l][r][k];
+    }
+}
