LeetCode -- Letter Combinations of a Phone Number

public class Solution {
    public IList<string> LetterCombinations(string digits) 
    {
      	if(string.IsNullOrWhiteSpace(digits) || digits.Contains(‘1‘))
      	{
		    return new List<string>();
	    }
	
    	BuildMap();
    	
    	var all = new List<char[]>();
    	for(var i = 0;i < digits.Length; i++){
    		all.Add(dict[digits[i]]);
    	}
    	
    	var r = Find(all, 0);
    	
    	return r;
    }


private Dictionary<char, char[]> dict = new Dictionary<char, char[]>();


private IList<string> Find(IList<char[]> all, int row)
{
	if(row == all.Count - 1){
		var arr = new List<string>();
		for(var i = 0;i < all[all.Count -1].Length; i++){
			arr.Add(all[all.Count - 1][i].ToString());
		}
		return arr;
	}
	else{
		var children = Find(all, row + 1);
		var arr = new List<string>();
		for(var i = 0;i < all[row].Length; i++){
			var self = all[row][i];
			for(var j = 0;j < children.Count; j++){
				arr.Add(self + children[j]);
			}
		}
		
		return arr;
	}
}




private void BuildMap(){
	dict.Add(‘2‘, new char[3]{‘a‘,‘b‘,‘c‘});
	dict.Add(‘3‘, new char[3]{‘d‘,‘e‘,‘f‘});
	dict.Add(‘4‘, new char[3]{‘g‘,‘h‘,‘i‘});
	dict.Add(‘5‘, new char[3]{‘j‘,‘k‘,‘l‘});
	dict.Add(‘6‘, new char[3]{‘m‘,‘n‘,‘o‘});
	dict.Add(‘7‘, new char[4]{‘p‘,‘q‘,‘r‘,‘s‘});
	dict.Add(‘8‘, new char[3]{‘t‘,‘u‘,‘v‘});
	dict.Add(‘9‘, new char[4]{‘w‘,‘x‘,‘y‘,‘z‘});
}
}

LeetCode -- Letter Combinations of a Phone Number

原文：http://blog.csdn.net/lan_liang/article/details/49108367