https://leetcode-solutions-5zk.pages.dev/tags/combinatorics/Recent content in Combinatorics on LeetCode 题解笔记Hugozh-cn2026 ZenzZweiMon, 11 May 2026 12:12:02 +0800https://leetcode-solutions-5zk.pages.dev/posts/2338-count-the-number-of-ideal-arrays/Thu, 30 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2338-count-the-number-of-ideal-arrays/Hard | Math, Dynamic Programming, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/2400-number-of-ways-to-reach-a-position-after-exactly-k-steps/Thu, 30 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2400-number-of-ways-to-reach-a-position-after-exactly-k-steps/Medium | Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/1916-count-ways-to-build-rooms-in-an-ant-colony/Wed, 29 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1916-count-ways-to-build-rooms-in-an-ant-colony/Hard | Array, Math, Dynamic Programming, Tree, Depth-First Search, Graph Theory, Topological Sort, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3577-count-the-number-of-computer-unlocking-permutations/Wed, 29 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3577-count-the-number-of-computer-unlocking-permutations/Medium | Array, Math, Brainteaser, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3250-find-the-count-of-monotonic-pairs-i/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3250-find-the-count-of-monotonic-pairs-i/Hard | Array, Math, Dynamic Programming, Combinatorics, Prefix Sumhttps://leetcode-solutions-5zk.pages.dev/posts/3251-find-the-count-of-monotonic-pairs-ii/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3251-find-the-count-of-monotonic-pairs-ii/Hard | Array, Math, Dynamic Programming, Combinatorics, Prefix Sumhttps://leetcode-solutions-5zk.pages.dev/posts/3272-find-the-count-of-good-integers/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3272-find-the-count-of-good-integers/Hard | Hash Table, Math, Combinatorics, Enumerationhttps://leetcode-solutions-5zk.pages.dev/posts/3312-sorted-gcd-pair-queries/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3312-sorted-gcd-pair-queries/Hard | Array, Hash Table, Math, Binary Search, Combinatorics, Counting, Number Theory, Prefix Sumhttps://leetcode-solutions-5zk.pages.dev/posts/3317-find-the-number-of-possible-ways-for-an-event/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3317-find-the-number-of-possible-ways-for-an-event/Hard | Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3343-count-number-of-balanced-permutations/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3343-count-number-of-balanced-permutations/Hard | Math, String, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3352-count-k-reducible-numbers-less-than-n/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3352-count-k-reducible-numbers-less-than-n/Hard | Math, String, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3395-subsequences-with-a-unique-middle-mode-i/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3395-subsequences-with-a-unique-middle-mode-i/Hard | Array, Hash Table, Math, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3405-count-the-number-of-arrays-with-k-matching-adjacent-elements/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3405-count-the-number-of-arrays-with-k-matching-adjacent-elements/Hard | Math, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3426-manhattan-distances-of-all-arrangements-of-pieces/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3426-manhattan-distances-of-all-arrangements-of-pieces/Hard | Math, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3428-maximum-and-minimum-sums-of-at-most-size-k-subsequences/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3428-maximum-and-minimum-sums-of-at-most-size-k-subsequences/Medium | Array, Math, Dynamic Programming, Sorting, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3461-check-if-digits-are-equal-in-string-after-operations-i/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3461-check-if-digits-are-equal-in-string-after-operations-i/Easy | Math, String, Simulation, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/3463-check-if-digits-are-equal-in-string-after-operations-ii/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3463-check-if-digits-are-equal-in-string-after-operations-ii/Hard | Math, String, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/3470-permutations-iv/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3470-permutations-iv/Hard | Array, Math, Combinatorics, Enumerationhttps://leetcode-solutions-5zk.pages.dev/posts/3518-smallest-palindromic-rearrangement-ii/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3518-smallest-palindromic-rearrangement-ii/Hard | Hash Table, Math, String, Combinatorics, Countinghttps://leetcode-solutions-5zk.pages.dev/posts/3539-find-sum-of-array-product-of-magical-sequences/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3539-find-sum-of-array-product-of-magical-sequences/Hard | Array, Math, Dynamic Programming, Bit Manipulation, Combinatorics, Bitmaskhttps://leetcode-solutions-5zk.pages.dev/posts/3621-number-of-integers-with-popcount-depth-equal-to-k-i/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3621-number-of-integers-with-popcount-depth-equal-to-k-i/Hard | Math, Dynamic Programming, Bit Manipulation, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3725-count-ways-to-choose-coprime-integers-from-rows/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3725-count-ways-to-choose-coprime-integers-from-rows/Hard | Array, Math, Dynamic Programming, Matrix, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/3757-number-of-effective-subsequences/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3757-number-of-effective-subsequences/Hard | Array, Math, Dynamic Programming, Bit Manipulation, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3821-find-nth-smallest-integer-with-k-one-bits/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3821-find-nth-smallest-integer-with-k-one-bits/Hard | Math, Bit Manipulation, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3855-sum-of-k-digit-numbers-in-a-range/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3855-sum-of-k-digit-numbers-in-a-range/Hard | Math, Divide and Conquer, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/3881-direction-assignments-with-exactly-k-visible-people/Mon, 27 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3881-direction-assignments-with-exactly-k-visible-people/Medium | Math, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/2963-count-the-number-of-good-partitions/Sun, 26 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2963-count-the-number-of-good-partitions/Hard | Array, Hash Table, Math, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3116-kth-smallest-amount-with-single-denomination-combination/Sun, 26 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3116-kth-smallest-amount-with-single-denomination-combination/Hard | Array, Math, Binary Search, Bit Manipulation, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/3128-right-triangles/Sun, 26 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3128-right-triangles/Medium | Array, Hash Table, Math, Combinatorics, Countinghttps://leetcode-solutions-5zk.pages.dev/posts/3154-find-number-of-ways-to-reach-the-k-th-stair/Sun, 26 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3154-find-number-of-ways-to-reach-the-k-th-stair/Hard | Math, Dynamic Programming, Bit Manipulation, Memoization, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/3179-find-the-n-th-value-after-k-seconds/Sun, 26 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/3179-find-the-n-th-value-after-k-seconds/Medium | Array, Math, Simulation, Combinatorics, Prefix Sumhttps://leetcode-solutions-5zk.pages.dev/posts/2842-count-k-subsequences-of-a-string-with-maximum-beauty/Sat, 25 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2842-count-k-subsequences-of-a-string-with-maximum-beauty/Hard | Hash Table, Math, String, Greedy, Sorting, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/2928-distribute-candies-among-children-i/Sat, 25 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2928-distribute-candies-among-children-i/Easy | Math, Combinatorics, Enumerationhttps://leetcode-solutions-5zk.pages.dev/posts/2929-distribute-candies-among-children-ii/Sat, 25 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2929-distribute-candies-among-children-ii/Medium | Math, Combinatorics, Enumerationhttps://leetcode-solutions-5zk.pages.dev/posts/2930-number-of-strings-which-can-be-rearranged-to-contain-substring/Sat, 25 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2930-number-of-strings-which-can-be-rearranged-to-contain-substring/Medium | Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/2954-count-the-number-of-infection-sequences/Sat, 25 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2954-count-the-number-of-infection-sequences/Hard | Array, Math, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/2063-vowels-of-all-substrings/Fri, 24 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2063-vowels-of-all-substrings/Medium | Math, String, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/2221-find-triangular-sum-of-an-array/Fri, 24 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2221-find-triangular-sum-of-an-array/Medium | Array, Math, Simulation, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/2514-count-anagrams/Fri, 24 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2514-count-anagrams/Hard | Hash Table, Math, String, Combinatorics, Countinghttps://leetcode-solutions-5zk.pages.dev/posts/2597-the-number-of-beautiful-subsets/Fri, 24 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/2597-the-number-of-beautiful-subsets/Medium | Array, Hash Table, Math, Dynamic Programming, Backtracking, Sorting, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/1359-count-all-valid-pickup-and-delivery-options/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1359-count-all-valid-pickup-and-delivery-options/Hard | Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/1467-probability-of-a-two-boxes-having-the-same-number-of-distinct-balls/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1467-probability-of-a-two-boxes-having-the-same-number-of-distinct-balls/Hard | Array, Math, Dynamic Programming, Backtracking, Combinatorics, Probability and Statisticshttps://leetcode-solutions-5zk.pages.dev/posts/1569-number-of-ways-to-reorder-array-to-get-same-bst/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1569-number-of-ways-to-reorder-array-to-get-same-bst/Hard | Array, Math, Divide and Conquer, Dynamic Programming, Tree, Union-Find, Binary Search Tree, Memoization, Combinatorics, Binary Treehttps://leetcode-solutions-5zk.pages.dev/posts/1621-number-of-sets-of-k-non-overlapping-line-segments/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1621-number-of-sets-of-k-non-overlapping-line-segments/Medium | Math, Dynamic Programming, Combinatorics, Prefix Sumhttps://leetcode-solutions-5zk.pages.dev/posts/1641-count-sorted-vowel-strings/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1641-count-sorted-vowel-strings/Medium | Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/1643-kth-smallest-instructions/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1643-kth-smallest-instructions/Hard | Array, Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/1735-count-ways-to-make-array-with-product/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1735-count-ways-to-make-array-with-product/Hard | Array, Math, Dynamic Programming, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/1830-minimum-number-of-operations-to-make-string-sorted/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1830-minimum-number-of-operations-to-make-string-sorted/Hard | Hash Table, Math, String, Combinatorics, Countinghttps://leetcode-solutions-5zk.pages.dev/posts/1863-sum-of-all-subset-xor-totals/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1863-sum-of-all-subset-xor-totals/Easy | Array, Math, Backtracking, Bit Manipulation, Combinatorics, Enumerationhttps://leetcode-solutions-5zk.pages.dev/posts/1866-number-of-ways-to-rearrange-sticks-with-k-sticks-visible/Thu, 23 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1866-number-of-ways-to-rearrange-sticks-with-k-sticks-visible/Hard | Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/1201-ugly-number-iii/Wed, 22 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/1201-ugly-number-iii/Medium | Math, Binary Search, Combinatorics, Number Theoryhttps://leetcode-solutions-5zk.pages.dev/posts/0920-number-of-music-playlists/Wed, 22 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/0920-number-of-music-playlists/Hard | Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/0458-poor-pigs/Mon, 20 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/0458-poor-pigs/Hard | Math, Dynamic Programming, Combinatoricshttps://leetcode-solutions-5zk.pages.dev/posts/0062-unique-paths/Fri, 17 Apr 2026 00:00:00 +0000https://leetcode-solutions-5zk.pages.dev/posts/0062-unique-paths/Medium | Math, Dynamic Programming, Combinatorics