Computer Science Canada help with for loops please(add 1 to 100) |
| Author: | dmitrip [ Wed Feb 14, 2007 7:16 pm ] |
| Post subject: | help with for loops please(add 1 to 100) |
hello i am trying to write a program that will add up the first 100 positive integers and output the sum so like 1 + 2 + 3 + 4 + 5.....all the way to 100 this is what i got soo far [code] var counter,total : int counter := 1 for i :1..100 total := i + counter put total end for [code] can anybody please tell me what i can do from here thanks alot |
|
| Author: | neufelni [ Wed Feb 14, 2007 7:37 pm ] | ||
| Post subject: | Re: help with for loops please(add 1 to 100) | ||
You are making this more complicated than necessary. You don't need a counter variable, the i in the for loop acts as a counter variable. All you need is a total variable, initially set to 0. Then each time through the for loop you add the value of i to your total. Like this:
|
|||
| Author: | Cervantes [ Fri Feb 16, 2007 8:00 pm ] |
| Post subject: | RE:help with for loops please(add 1 to 100) |
Also, note that if you pair the first number with the last, the second with the second last, the third with the third last, and so on, you can get a formula. 1 + 2 + 3 + ... + 98 + 99 + 100 = (1+100) + (2+99) + (3+98) + ... + (49+52) + (50+51) = 101 + 101 + 101 + ... + 101 + 101 <<50 terms>> = 101 * 50 = 101 * (100 / 2) = n*(n+1) / 2 This is the formula that Guass developed to sum the first n natural numbers. No need for for loops! |
|
| Author: | Clayton [ Fri Feb 16, 2007 8:42 pm ] |
| Post subject: | Re: help with for loops please(add 1 to 100) |
does that formula only work with a range of natural numbers from 1 to n? |
|
| Author: | Cervantes [ Fri Feb 16, 2007 9:50 pm ] |
| Post subject: | RE:help with for loops please(add 1 to 100) |
Yes. However, if you want to sum up the numbers from, say 10 to 100, you'd just sum up the numbers from 1 to 100 then subtract the numbers from 1 to 9. |
|
| Author: | zylum [ Sat Feb 17, 2007 12:09 am ] | ||
| Post subject: | RE:help with for loops please(add 1 to 100) | ||
also note that these are triangle numbers.
|
|||