Print out the sum of 1/n-CodePudding

This is the C problem and i need your help.

I have checked my code lots of time but I can not print out the result. Question: input n and print out S = 1-1/2 1/3-1/4... -1/n with abs(1/n)>e

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
float checkQ3(int n){
    float sum = 0;
    for(int i = 0; i<= n; i  ){
        if(i % 2 == 0){
            sum  = -1/i;
        }else{
            sum  = 1/i;
        }
    }
    return sum;
}
int main(){
    int n; printf("Input n: "); scanf("%d",&n);
    float sum1 = checkQ3(n);
    printf("%f",sum1);
}

Then there is no ouput, I have tried so many way but it did not work,please help me.

CodePudding user response：

Your for loop starts at 0, rather than one resulting in division-by-zero. Edit your code to the following:

for(int i = 1; i<= n; i  ){
    if(i % 2 == 0){
        sum  = -1/i;
    }else{
        sum  = 1/i;
    }
}

CodePudding user response：

YOu need to distinguish

my program ran but gave the wrong result
my program crashed because I asked to do something impossible

Yours is the second one

I got

Unhandled exception at 0x00007FF695651997 in ConsoleApplication3.exe: 0xC0000094: Integer division by zero.

You must surely have got a similar error message too

Anyway run this code in your head with i == 0

for (int i = 0; i <= n; i  ) {
    if (i % 2 == 0) {
        sum  = -1 / i; <<<<<========

CodePudding user response：

Start your loop form 1 So that you don't face any exception

for (i = 1; i <= n; i  )
     s = i%2==0 ? -1/i : 1/i;

 return s;