如何防止循环中的最后计数被执行

How to prevent a final cout in a loop from being executed?

本文关键字：执行 最后 何防止 循环      更新时间：2023-10-16

我想写一个代码，给出给定整数的质因数分解。下面是我的代码:

#include <iostream>
#include <cmath>
using namespace std;
void primefactor(int a);
int main()
{
    int n;
    cout<<" Enter the value of n "<<endl;
    cin>>n;
    primefactor(n);
    return 0;
}
void primefactor(int a){
    while(a%2==0){
        cout<<"2*";
        a/=2;
    for(int i=3; i<=sqrt(a); i+=2){
        while(a%i==0){
            cout<<i<<"*";
            a=a/i;
        }
    }
    if(a>2){
        cout<<a<<endl;
    }
}

然而，当我在最后一个因子上运行输出时，我得到了一个额外的*因子分解。我怎样才能去掉这个?

可以使用

if (a != 2)
    cout<<"2*";
else
    cout<<"2";

代替cout<<"2*";

我有同样的问题，并解决了它与goto语句。

#include <iostream>
#include <math.h>
using namespace std;
void primeFactorization(int number) {
cout << number << ": ";
// WHILE number is even
while (number % 2 == 0) {
   // SET number = number / 2
    number = number / 2;
   // PRINT 2
    cout << 2 << " " ;
    // END WHILE
}
//  GOTO TERMINAL
reloop:
// FOR factor in 3 to the sqrt(number), by 2
for (int factor = 3; factor <= sqrt(number); factor = factor + 2) {
    // IF number modular factor equals 0 THEN
    if (number % factor == 0) {
    // PRINT factor
        cout << factor << " " ;
    // SET number = number / factor
        number = number / factor;
    // GOTO INITIAL 
        goto reloop;
    // END IF
    }
    // END FOR
}
//IF number > 2 THEN
if (number > 2) {
    //PRINT number
    cout << number;
    //END IF
}
cout << endl;
}
int main() {
int usersNumber;
bool userWants2Play = true;
while (userWants2Play) {
    
cout << "Please enter a number to be factored: " ;
cin >> usersNumber;
primeFactorization(usersNumber);
 
    cout << "Do you want to play again? 1 or 0: " ;
    cin >> userWants2Play;
}
return 0;
}
goto语句允许新的奇数再次通过循环。这样可以打印奇数素数因子，并且如果因子存在，则可以再次对新的旧数进行因子分解。
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