Sum Of Numbers

 find the sum of the given series. if the given number is n, the sum is 1+2+3+4+5.......+n.

Example 1:

Input:
N = 10
Output: 55
Explanation: For n = 10, sum will be 10+9+8+7+6+5+4+3+2+1=55

Example 2:

Input:
N = 5
Output: 15
Explanation: For n = 5, sum will be 1
+ 2 + 3 + 4 + 5 = 15.

Method 1:

First, a variable sum is initialized to 0. Then, the function enters a loop that continues while n is greater than 0. In each iteration of the loop, the current value of n is added to the sum, and then n is decremented by 1. Once the loop completes, the final value of the sum is returned.

java implementation:

class codemummy {
    long seriesSum(int n) {
        long sum=0;

        while(n>0){
            sum=sum+n;
            n--;
        }

        return sum;
    }
}

Time Complexity: O(n) 
space Complexity: O(1) 

c++ implementation:

long seriesSum(int n) {
    long sum=0;

    while(n>0){
        sum=sum+n;
        n--;
    }

    return sum;
}

Time Complexity: O(n) 
space Complexity: O(1) 

python implementation:

def seriesSum(n):
    sum = 0
    while n > 0:
        sum += n
        n -= 1
    return sum

Time Complexity: O(n) 
space Complexity: O(1) 

method 2 :

use formula:

java implementation:

class Solution {
    long seriesSum(int n) {
      long m=n;
      return (m*(m+1))/2;
    }
}

Time Complexity: O(1) 
space Complexity: O(1)

c++ implementation:

long seriesSum(int n) {
    long m = n;
    return (m * (m + 1)) / 2;
}

Time Complexity: O(1) 
space Complexity: O(1)

python implementation:

def seriesSum(n):
    return (n * (n + 1)) // 2

Time Complexity: O(1) 
space Complexity: O(1)