将输入的年月日转换成本年度的第几天

#include<iostream>
using namespace std;
int main()
{
	//将输入的年月日转换成本年度的第几天:
	int y = 0;
	int m = 0;
	int d = 0;
	cout << "请输入年月日:>" << endl;
	cin >> y >> m >> d;
	int arr[][13] = { {0,31,28,31,30,31,30,31,31,30,31,30,31},
				   {0,31,29,31,30,31,30,31,31,30,31,30,31} };
	//判断平年闰年:
	int i = (y % 4 == 0 && y % 100 != 0 || y % 400 == 0);	//i 1 闰年    i 0 平年
	int* p = arr[0];
	if (i)  p += 13;
	int j = 0;
	int sum = 0;
	for (j = 1; j <= m-1; j++)
	{
		sum += *(p + j);
	}
	sum = sum + d;
	cout << y << "年" << m << "月" << d << "日是本年度的第" << sum << "天" << endl;
	return 0;
}