# Pseudocode and flowchart to find the series of S= 1 - 3 + 5 - 7 + 9

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## Flowchart to find the series of number: ## Algorithm to find the series of number:

Declare i, sum, n and t; Read n; for i = 1 to i <= 2 * n - 1 incrementing i by 2 { sum = sum + i * t; If(i * t < 0) print i * t; else print + i * t; t = (-1) * t; } print sum;

Here in this algorithm we declare four variables as integer, n for storing the number, i for running the for loop, sum for storing the result and t for deciding if its positive(+1) or negative(-1).

Then we read the variable n and run the for loop from i=1 to n*2-1 representing the odd number like if we choose 5 then at the 5th number 9 should be there. And incrementing i by 2 as we need odd numbers we will start form 1 and add 2 to get odd number. Then using the if statement we will check if the number n is less than 0 or not. If yes then print as it is and if no print +i*t .We are doing this only to print the series as positive numbers do not come with + sign. For getting the sum we add sum of previous loop and odd number of this loop. For Eg. Let's take N =3 then loop will run from 1 to 5

• In the first iteration i=1 sum =1 and we print +1 and t becomes -1
• In the second iteration i=3 sum=1-3 as t is negative from the previous loop print -3 and t becomes 1
• In the third iteration i=5 sum =1-3+5 print 5 and t now becomes -1
Now we exit the loop as we have reached i = 5 and print the sum i.e. 3

## Implementation of the Program in C:

#include<stdio.h> int main() { int i, s = 0, n, t = 1; printf("N:"); scanf("%d", & n); for (i = 1; i <= 2 * n - 1; i += 2) { s = s + i * t; i * t < 0 ? printf(" %d ", i * t) : printf(" + %d ", i * t); t = (-1) * t; } printf(" \nSum is %d ", s); }

### Output of the program ## Struggling to Understand Algorithm and Flowchart? Try our Notes

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