欧拉计划（Project Euler）第十九题 matlab
原题目：
You are given the following information, but you may prefer to do some research for yourself.

• 1,Jan 1900 was a Monday.
• Thirty days has September,April, June and November.
  All the rest have thirty-one,
  Saving February alone,
  Which has twenty-eight, rain or shine.And on leap years, twenty-nine.
• A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.
  How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
  分析：
• 1900年一月1日为星期一；
• 一三五七八十腊是31天，其余除了二月，都是30天；
• 二月除了闰年都是28天，闰年29天。2000年虽然是世纪年，但是能被400整除，故也是闰年。
  计算范围是1901年一月1日到2000年十二月31日

sum=1;
a=[31 28 31 30 31 30 31 31 30 31 30 31];
b=0;
for year=1901:2000
    for i=1:12
    if mod(year,4)==0
        a(2)=29;
    end
    sum=sum+a(i);
    if mod(sum,7)==5
        b=b+1;
    end
    end
end
b   

最后输出结果是171