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Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 315: Count of Smaller Numbers After Self

Problem Restatement We are given an integer array nums . For each index i , count how many numbers to the right of nums[i] are smaller than nums[i] . Return an array counts , where: counts[i] = number of smaller elements to the right of nums[i] For example, in: nums = [5, 2, 6, 1] the answer is: [2, 1, 1, 0] because: Index Value Smaller values to the right...
leetcode array fenwick-tree binary-indexed-tree merge-sort May 10, 2026
Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 308: Range Sum Query 2D - Mutable

Problem Restatement We are given a 2D integer matrix. We need to implement a class called NumMatrix that supports two operations: Operation Meaning update(row, col, val) Change matrix[row][col] to val sumRegion(row1, col1, row2, col2) Return the sum of all cells inside the rectangle The rectangle is inclusive. Unlike LeetCode 304, the matrix can change after construction. So a fixed 2D prefix sum matrix is no longer enough. Input and Output...
leetcode matrix fenwick-tree binary-indexed-tree design May 10, 2026
Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 307: Range Sum Query - Mutable

Problem Restatement We are given an integer array nums . We need to implement a class called NumArray that supports two operations: Operation Meaning update(index, val) Change nums[index] to val sumRange(left, right) Return the sum from left through right , inclusive Unlike LeetCode 303, the array is mutable. Values can change after initialization. The official problem expects many updates and many range queries, so recomputing sums from scratch every time...
leetcode array fenwick-tree binary-indexed-tree segment-tree May 10, 2026
Wiki › Algorithms › 02. Data Structures › 2. Advanced Data Structures and Operations ›

2.3 Fenwick Tree Variants

2.3 Fenwick tree variants, 25 index slug name 1 fenwick-tree Fenwick Tree 2 fenwick-build Fenwick Build 3 fenwick-point-update Point Update 4 fenwick-prefix-query Prefix Query 5 fenwick-range-query Range Query 6 fenwick-range-update-point-query Range Update Point Query 7 fenwick-point-update-range-query Point Update Range Query 8 fenwick-range-update-range-query Range Update Range Query 9 fenwick-min-tree Fenwick Min Tree 10 fenwick-max-tree Fenwick Max Tree 11 fenwick-xor-tree Fenwick XOR Tree 12 fenwick-gcd-tree Fenwick GCD Tree 13 fenwick-2d 2D Fenwick...
algorithms data-structures fenwick-tree bit