Write a one line C function to round floating point numbers

Algorithm: roundNo(num)
1. If num is positive then add 0.5.
2. Else subtract 0.5.
3. Type cast the result to int and return.

Example:
num = 1.67, (int) num + 0.5 = (int)2.17 = 2
num = -1.67, (int) num – 0.5 = -(int)2.17 = -2

Implementation:

/* Program for rounding floating point numbers */
# include<stdio.h>

int roundNo(float num)
{
    return num < 0 ? num - 0.5 : num + 0.5;
}

int main()
{
    printf("%d", roundNo(-1.777));
    getchar();
    return 0;
}

Output: -2

Time complexity: O(1)
Space complexity: O(1)

Now try rounding for a given precision. i.e., if given precision is 2 then function should return 1.63 for 1.63322 and -1.63 for 1.6332.