这个题目思路比较好想，但是边界问题好难搞，测了好多次才成功。

题目

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.

For example,
Given “egg”, “add”, return true.

Given “foo”, “bar”, return false.

Given “paper”, “title”, return true.

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

解题思路

判断两个字符串是否同构
建立两个map，byteMap用于存储字符映射关系，一个用于存储被映射过的字符，保证一个字符不被映射两次（一一映射）

1. 遍历s,t, 判断s[i]是否存在byteMap中，如果存在，比较映射值和t[i]是否相等，如果相等，则继续下一次遍历，如果不等，说明两个字符串不同构
2. 如果s[i]不存在byteMap中，需要先判断s[i], t[i]的值是否相等，如果相等，把新增映射关系到Map中；如果不相等，需要判断t[i]是否存在于tMap中，如果存在，说明t[i]已经映射过一次，不能再次映射，返回false；如果不存在，则把新增映射关系到Map中
3. 如果所有s[i] -> t[i]都能保证一一映射，则返回true

代码

isomorphicStrings.go

package _205_Isomorphic_Strings

func IsIsomorphic(s string, t string) bool {
    var byteMap map[byte]byte
    byteMap = make(map[byte]byte)
    var tMap map[byte]bool
    tMap = make(map[byte]bool)

    len1 := len(s)

    for i := 0; i < len1; i++ {
        tmp, ok := byteMap[s[i]]
        if ok {
            if tmp != t[i] {
                return false
            }
        } else {
            if s[i] != t[i] {
                _, ok1 := tMap[t[i]]
                if ok1 {
                    return false
                }
            }

            byteMap[s[i]] = t[i]
            tMap[t[i]] = true
        }
    }

    return true
}

测试

isomorphicStrings_test.go

package _205_Isomorphic_Strings

import "testing"

func TestIsIsomorphic(t *testing.T) {
    var tests = []struct{
        s string
        t string
        output bool
    } {
        {"egg", "add", true},
        {"foo", "bar", false},
        {"paper", "title", true},
        {"ab", "aa", false},
        {"aa", "ab", false},
        {"aba", "baa", false},
    }

    for _, v := range tests {
        ret := IsIsomorphic(v.s, v.t)
        if ret == v.output {
            t.Logf("pass")
        } else {
            t.Errorf("fail, want %+v, get %+v", v.output, ret)
        }
    }
}