Update README.md

JavaCodeMing · JavaCodeMing · commit 8cf469c611da · 2020-08-24T20:13:40.000+08:00
diff --git a/README.md b/README.md
@@ -24,6 +24,7 @@
 45.[跳跃游戏 II(困难)/贪心算法](https://github.com/JavaCodeMing/LeetCode/blob/master/Algorithm/45.%E8%B7%B3%E8%B7%83%E6%B8%B8%E6%88%8F%20II(%E5%9B%B0%E9%9A%BE).md)   
 53.[最大子序和(简单)/动态规划](https://github.com/JavaCodeMing/LeetCode/blob/master/Algorithm/53.%E6%9C%80%E5%A4%A7%E5%AD%90%E5%BA%8F%E5%92%8C(%E7%AE%80%E5%8D%95).md)   
 55.[跳跃游戏(中等)/贪心算法](https://github.com/JavaCodeMing/LeetCode/blob/master/Algorithm/55.%E8%B7%B3%E8%B7%83%E6%B8%B8%E6%88%8F(%E4%B8%AD%E7%AD%89).md)   
+56.[合并区间(中等)/双指针](https://github.com/JavaCodeMing/LeetCode/blob/master/Algorithm/56.%E5%90%88%E5%B9%B6%E5%8C%BA%E9%97%B4(%E4%B8%AD%E7%AD%89).md)   
 84.[柱状图中最大的矩形(困难)/单调栈](https://github.com/JavaCodeMing/LeetCode/blob/master/Algorithm/84.%E6%9F%B1%E7%8A%B6%E5%9B%BE%E4%B8%AD%E6%9C%80%E5%A4%A7%E7%9A%84%E7%9F%A9%E5%BD%A2(%E5%9B%B0%E9%9A%BE).md)   
 85.[最大矩形(困难)/动态规划](https://github.com/JavaCodeMing/LeetCode/blob/master/Algorithm/85.%E6%9C%80%E5%A4%A7%E7%9F%A9%E5%BD%A2(%E5%9B%B0%E9%9A%BE).md)   
 94.[二叉树的中序遍历(中等)/递归/栈](https://github.com/JavaCodeMing/LeetCode/blob/master/Algorithm/94.%E4%BA%8C%E5%8F%89%E6%A0%91%E7%9A%84%E4%B8%AD%E5%BA%8F%E9%81%8D%E5%8E%86(%E4%B8%AD%E7%AD%89).md)   
