swift从0加到1000（不包括1000）的四种写法

var i = 0

var temp = 0

while i < 1000 {
    
    temp += i
    
    i++
}

println(temp)

var j = 0

var temp2 = 0

do {

    temp2 += j

    j++

} while (j < 1000)

println(temp2)

var temp3 = 0

for a in 0...999 {
    
    temp3 += a
}

println(temp3)

var temp4 = 0

for var b = 0; b < 1000; b++ {
    
    temp4 += b;
}

println(temp4)