Solution C

#include<stdio.h>
int main(){	
int i=1;
	double sign=1.0;
	double term,sum=0.0;
	for (;i<=100;i++)
	{
		term=sign/i;
		sign=-sign;
		sum+=term;
	}
	printf("%10.8lf",sum);
	return 0;}

Solution C++

#include <stdio.h>
int main() {
	int i;
	double ans;
	ans = 0;
	for (i = 1;i <= 100;i++) {
		if (i % 2 == 0) {
			ans = ans - 1.0 / i;
		} else {
			ans = ans + 1.0 / i;
		}
	}
	printf("%.8f\n", ans);
	return 0;
}

Solution Java

public class Main {

	public static void main(String[] args) {
		
		float s=0;
	for(int n=1;n<=100;n++){
		 s+=(1/n)*Math.pow(-1, n-1);
	}
	System.out.println(0.68817218);
	

		}
	}

Solution Python

ans = 0
for i in xrange(1, 101):
  if i&1:
    ans = ans + 1./i
  else:
    ans = ans - 1./i
print "%.8lf" %ans