撰寫一個程式，計算并顯示用戶輸入的正整數n的階乘

一直在課堂上研究這個問題。不知道我做錯了什么。

好像我只是沒有正確的格式。我的教授希望輸出看起來像“5!=1 * 2* 3* 4* 5=120”

有人可以幫我弄這個嗎？以下是我到目前為止所擁有的：

#include <iostream> 
#include <stdio.h>

int main() {
    int n, i, fact;

    printf("Enter a positive integer: \n");
   scanf("%d", &n);
    if (n < 0)
        printf("Error! Factorial of a negative number doesn't exist.");
    else {
        for( i = 1; i <= n;   i) {
            fact *= i;
            n= n * (n-1);
        }
        printf("Factorial of %d = ", &n, &fact) ;    
    }

    return 0;
}

uj5u.com熱心網友回復：

1. #include <iostream>如果是C代碼則洗掉
2. 使用函式。
3. 初始化區域變數（你沒有，這是未定義的行為）
4. 使用 C 編譯器編譯 C 程式

unsigned long long fact(unsigned val, char *buff)
{
    unsigned result = 1;
    *buff   = '1';
    *buff = 0;
    for(unsigned c = 2; c <= val; c  ) 
    {
        buff  = sprintf(buff, "x%u", c);
        result *= c;
    }
    return result;
}

int main(void)
{
    unsigned x;
    char y[1000];
    unsigned long long res;

    if(scanf("%u", &x) == 1){res = fact(x, y); printf("factoral(%u) = %s = %llu\n", x, y, res);}
    else printf("Invalid number!!!\n");
}

或沒有印刷步驟

unsigned long long fact(unsigned val)
{
    unsigned result;
    switch(val)
    {
        case 0: 
        case 1:
            result = 1;
            break;
        case 2:
            result = 2;
            break;
        default:
            result = 2;
            while(val > 2) result *= val--;
            break;
    }
    return result;
}

int main(void)
{
    unsigned x;

    if(scanf("%u", &x) == 1) printf("factioral(%u) = %llu\n", x, fact(x));
    else printf("Invalid number!!!\n");
}

https://godbolt.org/z/Tf5431zco

uj5u.com熱心網友回復：

對于初學者來說，將變數 n 宣告為有符號整數型別是沒有意義的。最好將其宣告為無符號整數型別。例如

unsigned int n, i, fact;

其次，變數 fact 沒有被初始化。您應該將其初始化為等于 1 的值。

所以上面的宣告可能看起來像

unsigned int n, i;
unsigned long long fact = 1;

在這個 for 回圈中

    for( i = 1; i <= n;   i) {
        fact *= i;
        n= n * (n-1);
    }

該宣告

        n= n * (n-1);

沒有意義，應洗掉。

在 printf 呼叫中，您必須使用變數的值而不是指向變數的指標，例如

printf("Factorial of %u = %llu\n", n, fact) ;

請注意<iostream>，您的程式中沒有使用頭檔案中的宣告，因此無論是 C 程式還是 C 程式，都請洗掉此頭檔案。

這是一個演示 C 程式。

#include <stdio.h>

int main( void )
{
    unsigned int n = 0;
    unsigned long long int fact = 1;

    printf( "Enter a positive integer: " );
    scanf( "%u", &n );

    printf( "%u! = ", n );

    for ( unsigned int i = 1; i <= n; i   )
    {
        fact *= i;

        if ( i != 1 ) printf( " * " );

        printf( "%u", i );
    }

    printf( " = %llu\n", fact );
}

The program output might look like

Enter a positive integer: 5
5! = 1 * 2 * 3 * 4 * 5 = 120

If you are allowed to use only variables of the type int as you wrote in a comment to the answer then the program can look like

#include <stdio.h>

int main( void )
{
    int n = 0;
    int fact = 1;

    printf( "Enter a positive integer: " );
    scanf( "%d", &n );

    if  ( n  <  0 )
    {
        puts( "Error! Factorial of a negative number doesn't exist."); 
    }
    else 
    {
        printf( "%d! = ", n );

        for ( int i = 1; i <= n; i   )
        {
            fact *= i;

            if ( i != 1 ) printf( " * " );

            printf( "%d", i );
        }

        printf( " = %d\n", fact );
    }   
}

To output multipliers in the reverse order like

5! = 5 * 4 * 3 * 2 * 1 = 120

rewrite the for loop the following way

    for ( int i = n; i != 0; i-- )
    {
        fact *= i;

        if ( i != n ) printf( " * " );

        printf( "%d", i );
    }

標籤：C 循环 for循环 打印输出 阶乘

上一篇：ReactNative[TypeError:undefinedisnotanobject(evaluating'iter[Symbol.iterator]')]錯誤

下一篇：使用函式編碼字串