feixiangcode
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+//
+//  LeetCode_720_031.swift
+//  TestCoding
+//
+//  Created by 龚欢 on 2019/5/11.
+//  Copyright © 2019 龚欢. All rights reserved.
+//
+
+import Foundation
+
+class Solution {
+    func longestWord(_ words: [String]) -> String {
+        let sortedWords = Set(words).sorted {
+            if $0.count == $1.count {
+                return $0 < $1
+            } else {
+                return $0.count > $1.count
+            }
+        }
+        var errorDatas: Set<String> = []
+        for key in sortedWords {
+            if (errorDatas.contains(key)) { continue }
+            for i in 1...key.count {
+                let subString = String(key[key.startIndex..<key.index(key.startIndex, offsetBy: i)])
+                if (sortedWords.contains(subString)) {
+                    if i == key.count { return key }
+                    continue
+                } else {
+                    errorDatas.insert(key)
+                    break
+                }
+            }
+        }
+        return ""
+    }
+}