[LeetCode] 1053. Previous Permutation With One Swap
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Given an array of positive integers arr
(not necessarily distinct), return the lexicographically largest permutation that is smaller than arr
, that can be made with exactly one swap (A swap exchanges the positions of two numbers arr[i]
and arr[j]
). If it cannot be done, then return the same array.
Example 1:
Input: arr = [3,2,1] Output: [3,1,2] Explanation: Swapping 2 and 1.
Example 2:
Input: arr = [1,1,5] Output: [1,1,5] Explanation: This is already the smallest permutation.
Example 3:
Input: arr = [1,9,4,6,7] Output: [1,7,4,6,9] Explanation: Swapping 9 and 7.
Example 4:
Input: arr = [3,1,1,3] Output: [1,3,1,3] Explanation: Swapping 1 and 3.
Constraints:
1 <= arr.length <= 104
1 <= arr[i] <= 104
交换一次的先前排列。
给你一个正整数的数组 A(其中的元素不一定完全不同),请你返回可在 一次交换(交换两数字 A[i] 和 A[j] 的位置)后得到的、按字典序排列小于 A 的最大可能排列。
如果无法这么操作,就请返回原数组。
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/previous-permutation-with-one-swap
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这道题有两种思路,一种会利用到treemap,一种是线性解法。
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