DP and back trace solution in C++


  • 2
    H

    m[len][i] record if s start from i with length len is a valid palindrome.
    logic for back trace part is:
    i start from b to n, if s[b..i] is a palindrome, push_back to tmp result, go ahead

    void partition(string s, int b, int n, vector<int>& ret, vector<vector<bool> >& m,vector<vector<string> >& res) {
        if(b==n)
        {
    		vector<string> vs;
    		int k=0;
            for(int i=0;i<ret.size();i++)
    		{
    			vs.push_back(s.substr(k,ret[i]-k+1));
    			k=ret[i]+1;
    		}
    		res.push_back(vs);
        }
        for(int i=b; i<n; i++)
        {
            if(m[i-b+1][b])
            {
    			ret.push_back(i);
                partition(s,i+1,n,ret, m ,res);
    			ret.pop_back();
            }
        }
    }
    vector<vector<string>> partition(string s) {
        int n=s.length();
    	vector<vector<bool> > m(n+1, vector<bool>(n,false));
    
    	for(int len=1;len<=n;len++)
    	{
    		for(int i=0;i<=n-len;i++)
    		{
    			if(len==1)m[len][i]=true;
    			else if(len==2)m[len][i]=s[i]==s[i+1];
    			else
    			{
    				
    				m[len][i]=m[len-2][i+1]&&s[i]==s[i+len-1];
    			}
    		}
    	}
    	vector<vector<string>> res;
    	vector<int> ret;
        partition(s,0,n,ret,m,res);
    	return res;
    }

Log in to reply
 

Looks like your connection to LeetCode Discuss was lost, please wait while we try to reconnect.