leetcode 290 Word Pattern

原题：

Given a pattern and a string str, find if str follows the same pattern.

Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str.

Examples:

pattern = “abba”, str = “dog cat cat dog” should return true.

pattern = “abba”, str = “dog cat cat fish” should return false.

pattern = “aaaa”, str = “dog cat cat dog” should return false.

pattern = “abba”, str = “dog dog dog dog” should return false.

Notes:

You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

题意：

给你一个模式串和一个字符串，其中模式串中一个字母代表一种字符串，现在问你字符串和模式串能不能匹配上。

[code]class Solution
{
    map<char,string> mc;
    map<string,char> ms;
    vector<string> vs;
public:
    bool wordPattern(string pattern, string str)
    {
        mc.clear();
        ms.clear();
        vs.clear();
        str+=" ";
        int pos=0;
        for(int j=0;j<str.size();j++)
        {
            if(str[j]==' ')
            {
                string tmp=str.substr(pos,j-pos);
                pos=j+1;
                vs.push_back(tmp);
            }
        }
        if(vs.size()!=pattern.size())
            return false;
        for(int i=0;i<pattern.size();i++)
        {
            char c=pattern[i];
            if(mc[c]==""&&ms[vs[i]]==0)
            {
                mc[c]=vs[i];
                ms[vs[i]]=c;
            }
            else
            {
                if(mc[c]!=vs[i]||ms[vs[i]]!=c)
                    return false;
            }
        }
        return true;
    }
};

解答：

首先把给的字符串按空格拆开存起来，然后建立两个映射表，一个是模式串中的字符对应于单词，另一个是单词对应模式串里的字符。首先，如果模式串里的字母数和单词的数量不对应那肯定是false，否则判断双向映射是否匹配即可~