[Swift]LeetCode205. 同构字符串 | Isomorphic Strings

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Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

Example 1:

"egg", 
"add"

Example 2:

"foo", 
"bar"

Example 3:

"paper", 
"title"

Note:
You may assume both s and t have the same length.

---

给定两个字符串 s 和 t，判断它们是否是同构的。

如果 s 中的字符可以被替换得到 t ，那么这两个字符串是同构的。

所有出现的字符都必须用另一个字符替换，同时保留字符的顺序。两个字符不能映射到同一个字符上，但字符可以映射自己本身。

示例 1:

"egg", 
"add"

示例 2:

"foo", 
"bar"

示例 3:

"paper", 
"title"

说明:
你可以假设 s 和 t 具有相同的长度。

---

 28ms

class Solution {
  func isIsomorphic(_ s: String, _ t: String) -> Bool {
    let s = Array(s)
    let t = Array(t)
    
    var dict: [Character: Character] = [:]
    
    for i in 0..<s.count {
      if let cache = dict[s[i]] {
        if cache != t[i] {
          return false
        }
      } else if dict.values.contains(t[i]) {
        return false
      } else {
        dict[s[i]] = t[i]
      }
    }
    
    return true
  }
}

---

28ms

class Solution {
    func isIsomorphic(_ s: String, _ t: String) -> Bool {
        guard s.count == t.count else {
            return false
        }
        
        var map: [Character: Character] = [:]
        var set: Set<Character> = []
        var charsS = Array(s)
        var charsT = Array(t)
        for index in 0..<s.count {
            let charS = charsS[index]
            let charT = charsT[index]
            if let char = map[charS] {
                if char != charT {
                    return false
                }
            } else {
                if set.contains(charT) {
                    return false
                }
                
                map[charS] = charT
                set.insert(charT)
            }
        }
        
        return true
    }
}

---

32ms

class Solution {
    func isIsomorphic(_ s: String, _ t: String) -> Bool {
        let s = Array(s)
        let t = Array(t)
        if s.count != t.count { return false }
        
        var isoMap1 = [Character:Character]()
        var isoMap2 = [Character:Character]()
        
        var index = 0
        
        while index < s.count {
            
            let c1 = s[index]
            let c2 = t[index]
            
            if let saved = isoMap1[c1] {
                if saved != c2 {
                    return false
                }
            } else {
                isoMap1[c1] = c2
            }
            
            if let saved = isoMap2[c2] {
                if saved != c1 {
                    return false
                }
            } else {
                isoMap2[c2] = c1
            }
            index += 1
        }
        return true
    }
}

---

36ms

class Solution {
    func isIsomorphic(_ s: String, _ t: String) -> Bool {
        var m1 = [Int](repeating: 0, count: 256)
        var m2 = [Int](repeating: 0, count: 256)
        var s = Array(s)
        var t = Array(t)
    
        for i in 0..<s.count {
            let sAscii = Int(s[i].unicodeScalars.first?.value ?? 0)
            let tAscii = Int(t[i].unicodeScalars.first?.value ?? 0)
            if m1[sAscii] != m2[tAscii] {
                return false
            }
            m1[sAscii] = i + 1
            m2[tAscii] = i + 1
        }
    
        return true
    }
}

---

44ms

class Solution {
    func isIsomorphic(_ s: String, _ t: String) -> Bool {
        var s0 = Array(s)
        var t0 = Array(t)
        var dic = [Character : Character]()
        
        
        for i in 0..<s0.count {
            let s1 = s0[i]
            let t1 = t0[i]
            if let tmp = dic[s1]  {
                if tmp == t1 {
                    continue
                }else {
                    return false
                }
            }else {
                if dic.values.contains(t1) {
                    return false
                }
                dic[s1] = t1
            }
        }
        
        return true
    }
}

---

52ms

class Solution {
    func isIsomorphic(_ s: String, _ t: String) -> Bool {
        var mapS = [Character:Character]()
        var mapT = [Character:Character]()
        for idx in 0 ..< s.count {
            let cs = s[String.Index.init(encodedOffset: idx)]
            let ct = t[String.Index.init(encodedOffset: idx)]
            
            if let c = mapT[ct] {
                if c != cs {
                    return false
                }
            } else {
                mapT[ct] = cs
            }
            
            if let c = mapS[cs] {
                if c != ct {
                    return false
                }
            } else {
                mapS[cs] = ct
            }
        }
        return true
    }
}