[leetcode]205. Isomorphic Strings

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:

Input: s = "egg", t = "add"
Output: true

Example 2:

Input: s = "foo", t = "bar"
Output: false

分析：

问两个字符串是否为同构字符串。同构字符串即两个字符串对应为构成相互映射，且同一个字符不能映射两个不同的字符，但是可以映射其本身。由于256个字符有Ascii码，所以定义2个长度为256初始值全为0的数组m1, m2。遍历原字符串，分别从源字符串和目标字符串取出一个字符，然后分别在两个数组中查找其值，若不相等，则返回false，若相等，将其值更新为i+1。

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        int m1[256] = {0};
        int m2[256] = {0};
        int len = s.size();
        for(int i=0; i<len; i++)
        {
            if(m1[s[i]] != m2[t[i]])
                return false;
            else
            {
                m1[s[i]] = i+1;
                m2[t[i]] = i+1;
            }
        }
        return true;      
    }
};