has_sum.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from __future__ import print_function


def has_sum(x, S):
    i = 0
    j = len(S) - 1
    while i < j:
        if S[i] + S[j] < x:
            i += 1
        elif S[i] + S[j] > x:
            j -= 1
        else:

            return True

    return False


if __name__ == '__main__':
    x = 56
    S = [1, 3, 4, 12, 22, 34, 98]  # На сортировку как раз потратили O(n*lg(n))
    print('Yes' if has_sum(x, S) else 'No')