用Swift写输入日期计算天数的Demo

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//输入XX年XX月XX日,计算出日期

// Playground - noun: a place where people can play
 import UIKit

func days (year: Int, month : Int, day : Int) ->(Int) {
    if (year < 0 || month < 0 || month > 12 || day < 0 || day > 31) {
        println("输入错误")
        return 0
    }
    var sum = 0
    var add = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334]
    switch month {
    case 1 :
        sum = day + add[month - 1]
    case 2 :
        sum = day + add[month - 1]
    case 3 :
        sum = day + add[month - 1]
    case 4 :
        sum = day + add[month - 1]
    case 5 :
        sum = day + add[month - 1]
    case 6 :
        sum = day + add[month - 1]
    case 7 :
        sum = day + add[month - 1]
    case 8 :
        sum = day + add[month - 1]
    case 9 :
        sum = day + add[month - 1]
    case 10 :
        sum = day + add[month - 1]
    case 11 :
        sum = day + add[month - 1]
    case 12 :
        sum = day + add[month - 1]
    default :
        println("输入错误")
    }
    if (year % 4 == 0 || (year % 400 == 0 && year % 100 != 0)) && (month > 2) {
        println("闰年")
        sum += 1
    }
    return sum;
}
days(1501, 3, 1)

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