川大2007年
1、求平均值的遞迴

float Average(float A[],int n) 
{
	if(n==0) return 0;
	if(n == 1)
	   return A[n-1];
    else
        return (A[n-1]+(n-1)*Average(A,n-1))/n;
}

2、字串轉換成整數

int Atol(char *strNum)
{
	int flag = 1;
	int i,n,num = 0 ;
	for(i = 0; strNum[i] != '\0';i++)
	{
		if(strNum[i] == '-')
			flag = -flag;
		if(strNum[i] >='0' && strNum[i] <= '9')
		{
			num = num * 10 + strNum[i] - '0';
		}
	}
	return flag == -1 ? -num : num;
}
 

3、實現拓撲排序

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <vector>


using namespace std;

int main()
{
    int n,m,x,y;
    cin>>n>>m;
    
    vector<vector<int>> v(n+1,vector<int>(n+1,0));
    vector<bool> visited(n+1,false);
	vector<int> res;
	vector<int> indegree(n+1,0);
	
	for(int i = 0 ; i < m; i++)
	{
		cin>>x>>y;
		v[x][y] = 1 ;
		indegree[y]++;
	}
	
	multiset<int> q;
	for(int i = 1 ; i <= n ; i++)
	{
		if(indegree[i] == 0 )
		{
			q.insert(i);
			visited[i] = true;
		}
	}
	
	while(!q.empty())
	{
		int cur = *q.begin();
		q.erase(q.begin());
		res.push_back(cur);
		
		for(int i = 0 ; i < v[cur].size(); i++)
		{
			if(v[cur][i] == 0) continue;
			if(--indegree[i] == 0 && !visited[i])
			{
				visited[i] = true;
				q.insert(i);
			}
		}
	}
	
	for(auto i :res)
	{
		cout<<i<<" ";
	}

    return 0;
}