数字之和 C++
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/7463507/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Sum of Numbers C++
提问by soniccool
I am supposed to write a program that asks the user for a positive integer value. The program should use a loop to get the sum of all the integers from 1 up to the number entered. For example, if the user enters 50, the loop will find the sum of 1, 2, 3, 4, ... 50.
我应该编写一个程序，要求用户输入一个正整数值。程序应该使用循环来获取从 1 到输入的数字的所有整数的总和。例如，如果用户输入 50，循环将找到 1、2、3、4、... 50 的总和。
But for some reason it is not working, i am having trouble with my for loops but this is what i have down so far.
但由于某种原因它不起作用，我的 for 循环有问题，但这就是我到目前为止所遇到的问题。
#include <iostream>
using namespace std;
int main()
{
int positiveInteger;
int startingNumber = 1;
int i = 0;
cout << "Please input an integer up to 100." << endl;
cin >> positiveInteger;
for (int i=0; i < positiveInteger; i++)
{
i = startingNumber + 1;
cout << i;
}
return 0;
}
I am just at a loss right now why it isn't working properly.
我现在不知道为什么它不能正常工作。
回答by Ernest Friedman-Hill
The loop is great; it's what's inside the loop that's wrong. You need a variable named sum, and at each step, add i+1to sum. At the end of the loop, sumwill have the right value, so print it.
循环很棒；这是循环内部的错误。您需要一个名为 的变量sum，并在每一步添加i+1到sum。在循环结束时，sum将具有正确的值，因此打印它。
回答by xxcv
try this:
尝试这个：
#include <iostream>
using namespace std;
int main()
{
int positiveInteger;
int startingNumber = 1;
cout << "Please input an integer upto 100." << endl;
cin >> positiveInteger;
int result = 0;
for (int i=startingNumber; i <= positiveInteger; i++)
{
result += i;
cout << result;
}
cout << result;
return 0;
}
回答by zackery.fix
I have the following formula that works without loops. I discovered it while trying to find a formula for factorials:
我有以下公式可以在没有循环的情况下工作。我在试图找到阶乘公式时发现了它：
#include <iostream>
using namespace std;
int main() {
unsigned int positiveInteger;
cout << "Please input an integer up to 100." << endl;
cin >> positiveInteger;
cout << (positiveInteger * (positiveInteger + 1)) / 2;
return 0;
}
回答by Jiri Kriz
You can try:
你可以试试：
int sum = startingNumber;
for (int i=0; i < positiveInteger; i++) {
sum += i;
}
cout << sum;
But much easier is to note that the sum 1+2+...+n = n*(n+1) / 2, so you do not need a loop at all, just use the formula n*(n+1)/2.
但是要注意 sum 容易得多1+2+...+n = n*(n+1) / 2，因此您根本不需要循环，只需使用公式即可n*(n+1)/2。
回答by Roland Illig
First, you have twovariables of the same name i. This calls for confusion.
首先，您有两个同名的变量i。这需要混淆。
Second, you should declare a variable called sum, which is initially zero. Then, in a loop, you should add to it the numbers from 1 upto and including positiveInteger. After that, you should output the sum.
其次，您应该声明一个名为 的变量sum，该变量最初为零。然后，在循环中，您应该向其中添加从 1 到包括 的数字positiveInteger。之后，您应该输出sum.
回答by rohit89
You are just updating the value of iin the loop. The value of ishould also be added each time.
您只是i在循环中更新 的值。的值i也应该每次添加。
It is never a good idea to update the value of iinside the forloop. The forloop index should only be used as a counter. In your case, changing the value of iinside the loop will cause all sorts of confusion.
i在for循环内部更新 的值从来都不是一个好主意。该for循环指数只应作为计数器。在您的情况下，更改i循环内的值会导致各种混乱。
Create variable totalthat holds the sum of the numbers up to i.
创建一个变量total来保存直到 的数字总和i。
So
所以
for (int i = 0; i < positiveInteger; i++)
total += i;
回答by Polaris878
mystycs, you are using the variable ito control your loop, howeveryou are editing the value of iwithin the loop:
mystycs，您正在使用变量i来控制循环，但是您正在编辑i循环内的值：
for (int i=0; i < positiveInteger; i++)
{
i = startingNumber + 1;
cout << i;
}
Try this instead:
试试这个：
int sum = 0;
for (int i=0; i < positiveInteger; i++)
{
sum = sum + i;
cout << sum << " " << i;
}
回答by Tony The Lion
int result = 0;
for (int i=0; i < positiveInteger; i++)
{
result = startingNumber + 1;
cout << result;
}
