#include #include "union_find_disjoint_set.hpp" #include "robust_assert.hpp" union_find_disjoint_set::union_find_disjoint_set(uint32_t size) noexcept { init(size); } void union_find_disjoint_set::init(uint32_t size) noexcept { parent.resize(size); std::iota(parent.begin(), parent.end(), 0u); } int32_t union_find_disjoint_set::find(uint32_t x) noexcept { while (parent[x] != x) { parent[x] = parent[parent[x]]; x = parent[x]; } return x; } int32_t union_find_disjoint_set::merge(uint32_t x, uint32_t y) noexcept { auto root_x = find(x), root_y = find(y); return parent[root_y] = parent[root_x]; } void union_find_disjoint_set::extract_disjoint_sets(stl_vector_mp>& disjoint_sets, stl_vector_mp& index_map) noexcept { const auto num_disjoint_set = parent.size(); index_map.resize(num_disjoint_set, INVALID_INDEX); uint32_t counter{}; // Assign each roots a unique index. for (uint32_t i = 0; i < num_disjoint_set; i++) { const auto root = find(i); if (root == i) { index_map[i] = counter; counter++; } } // Assign each element to its corresponding disjoint set. for (uint32_t i = 0; i < num_disjoint_set; i++) { const auto root = find(i); ROBUST_ASSERT(index_map[root] != INVALID_INDEX); index_map[i] = index_map[root]; } disjoint_sets.resize(counter); for (uint32_t i = 0; i < num_disjoint_set; i++) { const auto index = index_map[i]; disjoint_sets[index].emplace_back(i); } }