# Time Complexity where loop variable is incremented by 1, 2, 3, 4 ..

What is the time complexity of below code?

## C++

 `#include ` `using` `namespace` `std;`   `void` `fun(``int` `n) {` `    ``int` `j = 1, i = 0;` `    ``while` `(i < n) {` `        ``// Some O(1) task` `        ``i = i + j;` `        ``j++;` `    ``}` `}`

## C

 `void` `fun(``int` `n)` `{` `   ``int` `j = 1, i = 0;` `   ``while` `(i < n)` `   ``{` `       ``// Some O(1) task` `       ``i = i + j;` `       ``j++;` `   ``}` `}`

## Java

 `// Method with a parameter 'n'` `static` `void` `fun(``int` `n)` `{` `    ``// Initializing variables` `    ``int` `j = ``1``, i = ``0``;`   `    ``// While loop with condition` `    ``while` `(i < n) {` `        ``// Some O(1) task` `        ``i = i + j;` `        ``j++;` `    ``}` `}`

## Python3

 `def` `fun(n):` `    ``j, i ``=` `1``, ``0` `    ``while` `i < n:` `        ``# Some O(1) task` `        ``i ``=` `i ``+` `j` `        ``j ``+``=` `1`

## C#

 `using` `System;`   `static` `void` `fun(``int` `n)` `{` `    ``int` `j = 1, i = 0;` `    ``while` `(i < n) {` `        ``// Some O(1) task` `        ``i = i + j;` `        ``j++;` `    ``}` `}`

## Javascript

 `function` `fun(n) {` `    ``let j = 1,` `        ``i = 0;` `    ``while` `(i < n) {` `        ``// Some O(1) task` `        ``i = i + j;` `        ``j++;` `    ``}` `}`

The loop variable ‘i’ is incremented by 1, 2, 3, 4, … until i becomes greater than or equal to n. The value of i is x(x+1)/2 after x iterations. So if loop runs x times, then x(x+1)/2 < n. Therefore time complexity can be written as ?(?n).