[N-0] refactor 699

fishercoder1534 · fishercoder1534 · commit e6cd11d02f81 · 2017-11-04T16:46:55.000-07:00
diff --git a/README.md b/README.md
@@ -28,6 +28,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |714|[Best Time to Buy and Sell Stock with Transaction Fee](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-transaction-fee/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_714.java) | O(n) | O(1) | Medium | DP
 |713|[Subarray Product Less Than K](https://leetcode.com/problems/subarray-product-less-than-k/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_713.java) | O(n) | O(1) | Medium |
 |712|[Minimum ASCII Delete Sum for Two Strings](https://leetcode.com/problems/minimum-ascii-delete-sum-for-two-strings/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_712.java) | O(m*n) | O(m*n) | Medium | DP
+|699|[Falling Squares](https://leetcode.com/problems/falling-squares/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_699.java) | O(n^2) | O(n) | Hard | Segment Tree
 |698|[Partition to K Equal Sum Subsets](https://leetcode.com/problems/partition-to-k-equal-sum-subsets/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_698.java) | O(n*(2^n)) | O(2^n) | Medium | Backtracking
 |697|[Degree of an Array](https://leetcode.com/problems/degree-of-an-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_697.java) | O(n) | O(n) | Easy | 
 |696|[Count Binary Substrings](https://leetcode.com/problems/count-binary-substrings/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_696.java) | O(n) | O(n) | Easy | 
diff --git a/src/main/java/com/fishercoder/solutions/_699.java b/src/main/java/com/fishercoder/solutions/_699.java
@@ -1,5 +1,6 @@
 package com.fishercoder.solutions;
 
+import java.util.ArrayList;
 import java.util.List;
 
 /**
@@ -69,8 +70,42 @@
 
 public class _699 {
     public static class Solution1 {
+        /**credit: https://discuss.leetcode.com/topic/107107/easy-understood-o-n-2-solution-with-explanation*/
         public List<Integer> fallingSquares(int[][] positions) {
-            return null;
+            List<Interval> intervals = new ArrayList<>();
+            List<Integer> result = new ArrayList<>();
+            int height = 0;
+            for (int[] position : positions) {
+                Interval curr = new Interval(position[0], position[0] + position[1] - 1, position[1]);
+                height = Math.max(height, getHeight(intervals, curr));
+                result.add(height);
+            }
+            return result;
+        }
+
+        private int getHeight(List<Interval> intervals, Interval curr) {
+            int preMaxHeight = 0;
+            for (Interval interval : intervals) {
+                if (interval.end < curr.start || interval.start > curr.end) {
+                    continue;
+                }
+                preMaxHeight = Math.max(preMaxHeight, interval.height);
+            }
+            curr.height += preMaxHeight;
+            intervals.add(curr);
+            return curr.height;
+        }
+
+        class Interval {
+            int start;
+            int end;
+            int height;
+
+            public Interval(int start, int end, int height) {
+                this.start = start;
+                this.end = end;
+                this.height = height;
+            }
         }
     }
 }
diff --git a/src/test/java/com/fishercoder/_699Test.java b/src/test/java/com/fishercoder/_699Test.java
@@ -0,0 +1,29 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._699;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static junit.framework.TestCase.assertEquals;
+
+public class _699Test {
+    private static _699.Solution1 solution1;
+    private static int[][] positions;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _699.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        positions = new int[][]{
+                {1, 2},
+                {2, 3},
+                {6, 1}
+        };
+        assertEquals(Arrays.asList(2, 5, 5), solution1.fallingSquares(positions));
+    }
+}
