leetcode990——並查集

class Solution {
private:
    int fa[26];
public:
    int DFS(int x)
    {
        if(fa[x]!=x)
            fa[x]=DFS(fa[x]);
        return fa[x]; 
    }
    bool equationsPossible(vector<string>& equations) {
        int len=equations.size();
        for(int i=0;i<26;i++)
            fa[i]=i;
        for(int i=0;i<len;i++)
        {
            int x=equations[i][0]-'a';
            int y=equations[i][3]-'a';
            string op=equations[i].substr(1,2);
            if(op=="==")
            {
                fa[DFS(x)]=DFS(y);
            }    
        }
        for(int i=0;i<len;i++)
        {
            int x=equations[i][0]-'a';
            int y=equations[i][3]-'a';
            string op=equations[i].substr(1,2);
            if(op=="!=")
            {
                if(DFS(x)==DFS(y))
                {
                    return false;
                }
            }    
        }
        return true;
    }
};