Topic Collection of Zhejiang University Edition "C Language Programming (3rd Edition)"
Exercise 2-6 Find the sum of the first N terms in the factorial sequence (15 points)
This question requires writing a program to calculate the sum of the first N items of the sequence 1!+2!+3!+...
Input format:
Enter a positive integer N not exceeding 12 in one line.
Output format:
Output integer results in one line.
Input sample:
5
Sample output:
153
Code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
int N,S1=1,S=0;
scanf("%d",&N);
for (int j=N; j>=1; j--)
{
S1=1;
for (int i=j; i>=1; i--)
{
S1*=i;
}
S=S+S1;
}
printf("%d",S);
return 0;
}
to sum up:
for (int j=N; j>=1; j--)
{
S1=1;
for (int i=j; i>=1; i--)
{
S1*=i;
}
S=S+S1;
}
The outer loop is the number of control loops, and the inner for loop is used to find the factorial. After each factorial addition is calculated, S1 is defined as 1 through the external assignment to store the next factorial result.