LeetCode -- Course Schedule II

public class Solution {
    
public int[] FindOrder(int numCourses, int[,] prerequisites) 
{
	var row = prerequisites.GetLength(0);
	if(row == 0){
        int[] c = new int[numCourses];
        for(int i=0; i<numCourses; i++){
            c[i]=i;
        }
        return c;
    }
	
	// save [courseId, refCount]
	var refCountTable = new int[numCourses];
	
	for(var i = 0;i < row; i++){
		refCountTable[prerequisites[i,0]] ++;
	}
	
	// no ref courses
	var noRefCourses = new Dictionary<int, int>();
	for(var i = 0;i < row; i++){
		// find courses does not appear in ref table
		if(refCountTable[prerequisites[i,1]] == 0 && !noRefCourses.ContainsKey(prerequisites[i,1])){
			noRefCourses.Add(prerequisites[i,1],1);
		}
	}
	
	var size = noRefCourses.Count;
	
	var result = new int[numCourses];
	var count = 0;
	while(noRefCourses.Count > 0){
		var c = noRefCourses.Keys.First();
		result[count++] = c;
		noRefCourses.Remove(c);
		
		for(var i = 0;i < row; i++){
			if(prerequisites[i,1] == c){
				refCountTable[prerequisites[i,0]] --;
				
				if(refCountTable[prerequisites[i,0]] == 0 && !noRefCourses.ContainsKey(prerequisites[i,1])){
					noRefCourses.Add(prerequisites[i,0], 1);
					size++;
				}
			}
		}
	}
	
	if(size == numCourses){
		return result;
	}
	return new int[0];
	
}




}

LeetCode -- Course Schedule II

原文：http://blog.csdn.net/lan_liang/article/details/48650023