计算1！+2！+...+n!（多种方法求解）

阳光穿透心脏的1/2处 2022-12-24 01:59 373阅读 0赞

# 计算1！+2！+…+n! #

计算1！+2！+…+n!  
首先要学会计算n的阶乘  
在我以前介绍过n的阶乘求解的多种办法，可以翻以前的博客

附：用whlie循环计算n的阶乘

//计算n的阶乘
    #include<stdio.h>
    int main()
    { 
    	int num = 0;
    	int  i = 1;
    	int ret = 1;
    	printf("请输入一个数字：");
    	scanf("%d", &num);
    	if (num == 0)
    	{ 
    		printf("阶乘为：%d\n", ret);
    	}
    	else if (num<0)
    	{ 
    		printf("输入一个大于0的数字\n");
    	}
    	else
    	{ 
    		while (i<=num)
    		{ 
    			ret *= i;
    			++i;
    		}
    		printf("阶乘是：%d\n", ret);
    	}
    	return 0;
    
    }

## 计算1！+2！+…+n! ##

那么如何计算这种阶乘的和呢：

**1：利用双循环**

//计算1！+2！+...+n!
    //两次循环计算
    #include<stdio.h>
    int main()
    { 
    	int num = 0;
    	int  i = 1;
    	int j = 1;
    	int ret = 1;
    	int sum = 0;
    	printf("请输入一个数字：");
    	scanf("%d", &num);
    	if (num == 0)
    	{ 
    		printf("阶乘和为：%d\n", ret);
    	}
    	else if (num<0)
    	{ 
    		printf("输入一个大于0的数字\n");
    	}
    	else
    	{ 
    		while (i <= num)
    		{ 
    			while (j<=i)
    			{ 
    				ret *= i;
    				++j;
    			}
    			sum += ret;
    			++i;
    		}		
    		printf("阶乘和是：%d\n", sum);
    	}
    	return 0;
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MjE0MjczMQ_size_16_color_FFFFFF_t_70_pic_center]  
**2：一次循环**

//计算1！+2！+...+n!
    //一次循环计算
    #include<stdio.h>
    int main()
    { 
    	int num = 0;
    	int  i = 1;
    	int ret = 1;
    	int sum = 0;
    	printf("请输入一个数字：");
    	scanf("%d", &num);
    	if (num == 0)
    	{ 
    		printf("阶乘为：%d\n", ret);
    	}
    	else if (num<0)
    	{ 
    		printf("输入一个大于0的数字\n");
    	}
    	else
    	{ 
    		while (i <= num)
    		{ 
    			ret *= i;
    			++i;
    			sum += ret;
    		}
    		printf("阶乘是：%d\n", sum);
    	}
    	return 0;
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MjE0MjczMQ_size_16_color_FFFFFF_t_70_pic_center 1]

注意：  
**循环一定要有循环终止条件**

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