I am getting WA in Test case 2, particularly : wrong answer 35th numbers differ — expected: '1', found: '0'. I am unable to find the error in my code for this problem: 1622C - Set or Decrease My submission:193454039. The logic I used:

I have almost completed the Part1, should I do the whole part 2 or are there some advanced topics(steps) in there which i should avoid. I want to reach expert and want to be able to do 1400-1800 rating(if any) segment tree problems.

For this problem : https://www.spoj.com/problems/HAYBALE/ I submitted this solution: https://onlinegdb.com/-0MA4LwEE . This solution is giving TLE i.e. why I want to know the time complexity(with explanation).
My logic was to store all the K pairs in a map<int , vector> such that the first element of each pair acts as key , its value being a vector of all the values the key is making a pair with. Now I iterate from 1 till N(stack) and for each stack , I iterate through the keys which are less than or equal to the position of that stack . For each key , I binary search to find out In how many pairs my current stack is falling into. Finally I sort the array and the find the median.

My code is giving runtime error for all the cases that have n=1e5 and m = 2e5 input — Test cases 6 , 7 , 8 and 9 on the CSES website. Here is the submission: https://onlinegdb.com/ciDQleE8W

The answer is coming 0 instead of some positive value for some test cases Submission: https://codeforces.net/contest/1703/submission/164043486