From 47df32d855bfe2c5bb5e0e9904a8feaf419250c0 Mon Sep 17 00:00:00 2001
From: CRGT_Ghcoder <huan.gong@crgecent.com>
Date: Thu, 16 May 2019 22:22:09 +0800
Subject: [PATCH 1/2] add leetcode 211

---
 Week_04/id_31/LeetCode_211_031.swift | 53 ++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 Week_04/id_31/LeetCode_211_031.swift

diff --git a/Week_04/id_31/LeetCode_211_031.swift b/Week_04/id_31/LeetCode_211_031.swift
new file mode 100644
index 00000000..05745c31
--- /dev/null
+++ b/Week_04/id_31/LeetCode_211_031.swift
@@ -0,0 +1,53 @@
+//
+//  LeetCode_211_031.swift
+//  TestCoding
+//
+//  Created by 龚欢 on 2019/5/16.
+//  Copyright © 2019 龚欢. All rights reserved.
+//
+
+import Foundation
+
+class WordDictionary {
+    private class TrieNode {
+        var children: [Character: TrieNode] = [:]
+        var isEnd = false
+    }
+    
+    private let root: TrieNode
+    
+    init() {
+        root = TrieNode()
+    }
+    
+    func addWord(_ word: String) {
+        var node = root
+        for char in word {
+            if node.children[char] == nil {
+                node.children[char] = TrieNode()
+            }
+            node = node.children[char]!
+        }
+        node.isEnd = true
+    }
+    
+    func search(_ word: String) -> Bool {
+        return bfs(self.root, Array(word), 0)
+    }
+    
+    private func bfs(_ node: TrieNode, _ chars: [Character], _ nextIndex: Int) -> Bool {
+        if nextIndex == chars.count {
+            return node.isEnd
+        }
+        
+        for (nextChar, nextNode) in node.children {
+            if chars[nextIndex] == "." || chars[nextIndex] == nextChar {
+                if bfs(nextNode, chars, nextIndex + 1) {
+                    return true
+                }
+            }
+        }
+        
+        return false
+    }
+}

From 2d86bd6fad024a5e8e31389435d0eeb6a880855a Mon Sep 17 00:00:00 2001
From: CRGT_Ghcoder <huan.gong@crgecent.com>
Date: Mon, 20 May 2019 21:33:12 +0800
Subject: [PATCH 2/2] add leetcode 746

---
 Week_04/id_31/LeetCode_746_031.swift | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 Week_04/id_31/LeetCode_746_031.swift

diff --git a/Week_04/id_31/LeetCode_746_031.swift b/Week_04/id_31/LeetCode_746_031.swift
new file mode 100644
index 00000000..c88a803e
--- /dev/null
+++ b/Week_04/id_31/LeetCode_746_031.swift
@@ -0,0 +1,22 @@
+//
+//  LeetCode_746_031.swift
+//  TestCoding
+//
+//  Created by 龚欢 on 2019/5/20.
+//  Copyright © 2019 龚欢. All rights reserved.
+//
+
+import Foundation
+
+class Solution {
+    func minCostClimbingStairs(_ cost: [Int]) -> Int {
+        guard cost.count >= 2 else { return 0 }
+        var dp: [Int: Int] = [:]
+        dp[0] = cost[0]
+        dp[1] = cost[1]
+        for i in 2..<cost.count {
+            dp[i] = min(dp[i-1]!, dp[i-2]!) + cost[i]
+        }
+        return min(dp[cost.count - 1]!, dp[cost.count - 2]!)
+}
+