Graph

Graph/c_KruskalMST.c

@@ -0,0 +1,89 @@
+#include "c_KruskalMST.h"
+#include "c_MinPQ.h"
+#include "c_QuickFindUF.h" /* Direct inline layout consumption */
+
+
+/* ================================================================================================================== */
+/* Private Sort Comparator for c_MinPQ_t matching edge priorities */
+
+static int c_Kruskal_EdgeCompare(const void* a, const void* b, void* args) {
+    c_size_t id_a = *(const c_size_t*)a;
+    c_size_t id_b = *(const c_size_t*)b;
+    c_Edge_t* pool = (c_Edge_t*)args;
+
+    double weight_a = pool[id_a].weight;
+    double weight_b = pool[id_b].weight;
+
+    return (weight_a > weight_b) - (weight_a < weight_b);
+}
+
+/* ================================================================================================================== */
+/* Core Kruskal MST Initializer Processing Routine */
+
+c_err_t c_KruskalMST_Init(c_KruskalMST_t* self, c_EdgeWeightedGraph_t* graph, c_Allocator_t* allocator) {
+    if (!self || !graph) return C_ERR_PARAM;
+
+    self->allocator = allocator ? *allocator : c_DefaultAllocator;
+    self->weight = 0.0;
+    c_VertexIdList_Init(&self->mst_edges, 0, allocator);
+
+    if (graph->V == 0 || graph->E == 0) return C_SUCCESS;
+
+    /* 1. Build a priority queue containing all edge indices to sort them automatically */
+    c_MinPQ_t pq;
+    c_err_t err = c_MinPQ_Init(
+        &pq,
+        graph->E,
+        sizeof(c_size_t),
+        c_Kruskal_EdgeCompare,
+        graph->edges_pool,
+        allocator
+    );
+    if (err != C_SUCCESS) return err;
+
+    /* Seed the PQ with every single unique edge index */
+    for (c_size_t i = 0; i < graph->E; ++i) {
+        c_MinPQ_Push(&pq, &i);
+    }
+
+    /* 2. Configure your specific c_QuickFindUF data structure */
+    c_QuickFindUF_t uf;
+    err = c_QuickFindUF_Init(&uf, graph->V, allocator);
+    if (err != C_SUCCESS) {
+        c_MinPQ_Destroy(&pq);
+        return err;
+    }
+
+    /* 3. Main processing loop: extract edges in ascending order of weight */
+    while (!c_MinPQ_IsEmpty(&pq) && c_VertexIdList_GetSize(&self->mst_edges) < graph->V - 1) {
+        c_size_t edge_id = 0;
+        c_MinPQ_Pop(&pq, &edge_id);
+
+        c_Edge_t* edge = &graph->edges_pool[edge_id];
+        c_size_t v = edge->v;
+        c_size_t w = edge->w;
+
+        /* If v and w are not already connected, adding this edge is safe (no cycle created) */
+        if (!c_QuickFindUF_IsConnected(&uf, v, w)) {
+            c_QuickFindUF_Union(&uf, v, w);
+            c_VertexIdList_Append(&self->mst_edges, (c_uint_t)edge_id);
+            self->weight += edge->weight;
+        }
+    }
+
+    /* Clean up working structures */
+    c_QuickFindUF_Destroy(&uf);
+    c_MinPQ_Destroy(&pq);
+    return C_SUCCESS;
+}
+
+void c_KruskalMST_Destroy(c_KruskalMST_t* self) {
+    if (!self) return;
+    c_VertexIdList_Destroy(&self->mst_edges);
+    self->weight = 0.0;
+}
+
+c_err_t c_KruskalMST_GetEdges(c_KruskalMST_t* self, c_VertexIdList_t* out_edges) {
+    if (!self || !out_edges) return C_ERR_PARAM;
+    return c_VertexIdList_Copy(out_edges, &self->mst_edges);
+}