Розбір

Sort the programmers' ratings in the array $v$. To find two programmers with the maximum total rating, we'll use the two-pointer technique.

Initialize the pointer $low=0$ at the beginning of the array and the pointer $high=n-1$ at the end of the array.

Among all possible sums $v[low]+v[high]$, not exceeding $m$, find the maximum. If $v[low]+v[high]\le m$, move the $low$ pointer forward. Otherwise, move the $high$ pointer backward. Continue this process until the pointers meet.

Example

Let’s consider the second test. Sort the numbers and initialize the pointers. Simulate the algorithm’s execution. In this case, $m=19$: we are looking for two numbers with the maximum sum that does not exceed $19$.

Algorithm realization

Read the input data.

scanf("%d %d", &n, &m);
v.resize(n);
for (i = 0; i < n; i++)
  scanf("%d", &v[i]);

Sort the programmers’ ratings.

sort(v.begin(), v.end());

Initialize the pointers. The variable $mx$ stores the maximum sum of two elements.

int mx = -1, low = 0, high = n - 1;

The pointer $low$ is moved forward, and the pointer $high$ is moved backward.

while (low < high)
{

Among all possible sums $v[low]+v[high]$ that do not exceed $m$ find the maximum. If $v[low]+v[high]\le m$, move $low$ forward. Otherwise, move $high$ backward.

  if (v[low] + v[high] <= m)
  {
    mx = max(mx, v[low] + v[high]);
    low++;
  }
  else high--;
}

Print the answer.

printf("%d\n", mx);