Watching CPL Codechef January 2021 solution || Watching CPL codechef problem editorial 2021

 Watching CPL Codechef January 2021 solution || Watching CPL codechef problem editorial 2021-

Problem statement-

Get excited, folks, because it is time for the final match of Codechef Premier League (CPL)!

Mike and Tracy also want to watch the grand finale, but unfortunately, they could not get tickets to the match. However, Mike is not someone who gives up so easily — he has a plan to watch the match.

The field where the match is played is surrounded by a wall with height K$K$. Outside, there are N$N$ boxes (numbered 1 $1$ through N$N$). For each valid i$i$, the i$i$-th box has a height Hi$H_i$.

Mike wants to take some boxes and stack them on top of each other to build two towers. The height of each tower is the sum of heights of all the boxes that form it. Of course, no box may be in both towers. The height of each tower should be at least K$K$. Then Mike can climb on top of one tower and Tracy on top of the other, and they can watch the match uninterrupted!

While Mike is busy stacking the boxes, Tracy would like to know the smallest number of boxes required to build two towers such that each of them has height at least K$K$, or at least that it is impossible to build such towers. Can you help Tracy?

Input

• The first line of the input contains a single integer T$T$ denoting the number of test cases. The description of T$T$ test cases follows.
• The first line of each test case contains two space-separated integers N$N$ and K$K$.
• The second line contains N$N$ space-separated integers H1,H2,…,HN$H_1,H_2,\dots ,H_N$.

Output

For each test case, print a single line containing one integer — the smallest number of boxes required to build two towers, or −1$-1$ if it is impossible.

Constraints

• 1≤T≤5$1\le T\le 5$
• 1≤N,K≤4,000$1\le N,K\le 4,000$
• 1≤Hi≤105$1\le H_i\le {10}^5$ for each valid i$i$

Subtasks

Subtask #1 (30 points):

• 1≤N,K≤100$1\le N,K\le 100$
• 1≤Hi≤100$1\le H_i\le 100$ for each valid i$i$

Subtask #2 (70 points): original constraints

Example Input

2
8 38
7 8 19 7 8 7 10 20
4 5
2 10 4 9

Example Output

7
2

Explanation

Example case 1: The first tower can be built with boxes 8+10+20=38$8+10+20=38$ and the second tower with boxes 7+7+8+19=41$7+7+8+19=41$. In this case, the box with height 7$7$ is left unused.

Example case 2: We only need the box with height 10$10$ for one tower and the box with height 9$9$ for the other tower.

Solution -

Hint- other test cases.

8 15

10 7 7 5 1 1 1 1

output - 5

This problem is based on dynamic programming you need to learn the dynamic programming concept first.

where DP[i][k] represents minimum boxes required to make at least k hight till ith index.

we will use the suffix array here to find whether it is possible to make another box of height k. 

finally, we will print the optimal answer.

this question is similar to the 0/1 knapsack problem .

Refer this video  for better understanding -

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