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| Harbour.Space Scholarship Contest 2023-2024 (Div. 1 + Div. 2) |
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| Finished |
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Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ICPC mode for virtual contests.If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.
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constructive algorithms
greedy
sortings
strings
*1100
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- Custom test
B. Swap and Reverse
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
You are given a string $$$s$$$ of length $$$n$$$ consisting of lowercase English letters, and an integer $$$k$$$. In one step you can perform any one of the two operations below:
- Pick an index $$$i$$$ ($$$1 \le i \le n - 2$$$) and swap $$$s_{i}$$$ and $$$s_{i+2}$$$.
- Pick an index $$$i$$$ ($$$1 \le i \le n-k+1$$$) and reverse the order of letters formed by the range $$$[i,i+k-1]$$$ of the string. Formally, if the string currently is equal to $$$s_1\ldots s_{i-1}s_is_{i+1}\ldots s_{i+k-2}s_{i+k-1}s_{i+k}\ldots s_{n-1}s_n$$$, change it to $$$s_1\ldots s_{i-1}s_{i+k-1}s_{i+k-2}\ldots s_{i+1}s_is_{i+k}\ldots s_{n-1}s_n$$$.
You can make as many steps as you want (possibly, zero). Your task is to find the lexicographically smallest string you can obtain after some number of steps.
A string $$$a$$$ is lexicographically smaller than a string $$$b$$$ of the same length if and only if the following holds:
- in the first position where $$$a$$$ and $$$b$$$ differ, the string $$$a$$$ has a letter that appears earlier in the alphabet than the corresponding letter in $$$b$$$.
Input
Each test contains multiple test cases. The first line contains the number of test cases $$$t$$$ ($$$1 \le t \le 10^4$$$). The description of the test cases follows.
The first line of each test case contains two integers $$$n$$$ and $$$k$$$ ($$$1 \le k < n \le 10^5$$$).
The second line of each test case contains the string $$$s$$$ of length $$$n$$$ consisting of lowercase English letters.
It is guaranteed that the sum of $$$n$$$ over all test cases does not exceed $$$10^5$$$.
Output
For each test case, print the lexicographically smallest string after doing some (possibly, zero) steps.
Example
Input
5
4 2
nima
5 3
panda
9 2
theforces
7 3
amirfar
6 4
rounds
Output
aimnaandpceefhorstaafmirrdnorsu
Note
In the first test case, we can obtain the string "aimn" using the following operations:
- Reverse the range $$$[3,4]$$$. The string turns into "niam".
- Swap $$$s_1$$$ and $$$s_3$$$. The string turns into "ainm".
- Reverse the range $$$[3,4]$$$. The string turns into "aimn".
It can be proven that we cannot obtain any string lexicographically smaller than "aimn". Therefore, "aimn" is the answer.
In the second test case, we can obtain the string "aandp" using the following operations:
- Swap $$$s_3$$$ and $$$s_5$$$. The string turns into "paadn".
- Swap $$$s_1$$$ and $$$s_3$$$. The string turns into "aapdn".
- Swap $$$s_3$$$ and $$$s_5$$$. The string turns into "aandp".
It can be proven that we cannot obtain any string lexicographically smaller than "aandp". Therefore, "aandp" is the answer.
"); $(this).append($copy); const clipboard = new Clipboard('#' + cpyId, { text: function (trigger) { const pre = document.querySelector('#' + preId); const lines = pre.querySelectorAll(".test-example-line"); return Codeforces.filterClipboardText(pre.innerText, lines.length); } }); const isInput = $(this).parent().hasClass("input"); clipboard.on('success', function (e) { if (isInput) { Codeforces.showMessage("The example input has been copied into the clipboard"); } else { Codeforces.showMessage("The example output has been copied into the clipboard"); } e.clearSelection(); }); }); $(".test-form-item input").change(function () { addPendingSubmissionMessage($($(this).closest("form")), "You changed the answer, do not forget to submit it if you want to save the changes"); const index = $(this).closest(".problemindexholder").attr("problemindex"); let test = ""; $(this).closest("form input").each(function () { const test_ = $(this).attr("name"); if (test_ && test_.substring(0, 4) === "test") { test = test_; } }); if (index.length > 0 && test.length > 0) { const indexTest = index + "::" + test; window.changedTests.add(indexTest); } }); $(window).on('beforeunload', function () { if (window.changedTests.size > 0) { return 'Dialog text here'; } }); autosize($('.test-explanation textarea')); $(".test-example-line").hover(function() { $(this).attr("class").split(" ").forEach((clazz) => { if (clazz.substr(0, "test-example-line-".length) === "test-example-line-") { let end = clazz.substr("test-example-line-".length); if (end !== "even" && end !== "odd" && end !== "0") { let top = 1E20; let left = 1E20; let problem = $(this).closest(".problemindexholder"); $(this).closest(".input").find("." + clazz).css("background-color", "#FFFDE7").each(function() { top = Math.min(top, $(this).offset().top); left = Math.min(left, $(this).offset().left); }); let testCaseMarker = problem.find(".testCaseMarker_" + end); if (testCaseMarker.length === 0) { const html = "
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