How to find nearest integer to real, excluding integers from list?

Question

Algorithms

Given a real number, let's say float.
It is necessary to find the nearest integer that will not be in a separate list.

Examples:
1) There is a number 4.6. In a separate list, the number 5. The result should be 4.
2) There is a number 4.6. In a separate list of numbers 5, 4. The result should be 6.
3) There is a number 4.6. In a separate list, the numbers are 3, 4, 5, 6, 7. The result should be 2.

Answer 1

You round the number, check if it is in the array.
If not, the number is found.
If so, add/subtract from the number 1 and check again if it is in the array.
If not, the number is found.
If so, subtract / add 2 to the number and check again if it is in the array.
If not, the number is found.
If so, you add/subtract from the number 3 and check again if it is in the array.
Etc.
You alternate addition with subtraction (start depending on where it was rounded off) and at each iteration you increase the summand-subtracted by 1.