Create 587_Erect_the_Fence.java

587_Erect_the_Fence.java

@@ -0,0 +1,66 @@
+class Solution {
+    public int[][] outerTrees(int[][] trees) {
+        Arrays.sort(trees, new Comparator<int[]>() {
+            @Override
+            public int compare(int[] p, int[] q) {
+                return p[0] == q[0] ? q[1] - p[1] : p[0] - q[0];
+            }
+        });
+        Stack<int[]> stack = new Stack<>();
+        for (int i = 0; i < trees.length; i++){
+            int[] next = {trees[i][0],trees[i][1]};
+            while (stack.size() >= 2 && orientation(stack.get(stack.size() - 2), stack.peek(), next) > 0) {
+                stack.pop();
+            }
+            stack.push(next);
+        }
+        stack.pop();
+        for (int i = trees.length - 1; i >= 0; i--){
+            int[] next = {trees[i][0],trees[i][1]};
+            while (stack.size() >= 2 && orientation(stack.get(stack.size() - 2), stack.peek(), next) > 0) {
+                stack.pop();
+            }
+            stack.push(next);
+        }
+        int count = 0;
+        int dup_count = 0;
+        int[][] res = new int[stack.size()][];
+        for (int i = 0; i < stack.size(); i++)
+        {
+            int[] temp = stack.get(i);
+            res[count] = new int[2];
+            res[count][0] = temp[0];
+            res[count][1] = temp[1];
+            if (count >= 1)
+            {
+                int flag = 0;
+                for (int j = 0; j < count; j++)
+                {
+                    if (temp[0] == res[j][0] && temp[1] == res[j][1])
+                        flag = 1;
+                }
+                if (flag != 1)
+                    count++;
+                else
+                    dup_count++;
+            }
+            else
+            {
+                count++;
+            }
+        }
+        int[][] resAns = new int[count][];
+        for (int i = 0; i < count; i++)
+        {
+            resAns[i] = new int[2];
+            resAns[i][0] = res[i][0];
+            resAns[i][1] = res[i][1];
+        }
+        return resAns;
+    }
+
+    public int orientation(int[] p, int[] q, int[] r)
+    {
+        return (q[1] - p[1]) * (r[0] - p[0]) - (q[0] - p[0]) * (r[1] - p[1]);
+    }
+}