Dsa Graph Prim Mst

In this tutorial, you'll learn about How to Fix Prim's MST Errors. We cover key concepts, practical examples, and best practices.

Fix prim's mst errors when connected tracking wrong or edge weights not properly prioritized.

Quick Fix

Wrong

def prim(g):
    s=next(iter(g)); mst=[]; vis=set()
    pq=[(0,s,None)]
    while pq:
        w,u,p=heapq.heappop(pq)
        vis.add(u)
        if p: mst.append((p,u,w))
        for v,w in g[u]: heapq.heappush(pq,(w,v,u))

Adds all edges without checking if node already visited. Heavy memory.

Right

import heapq
def prim(g):
    s=next(iter(g)); mst=[]; vis={s}
    pq=[(w,s,v) for v,w in g[s]]; heapq.heapify(pq)
    while pq and len(vis)<len(g):
        w,u,v=heapq.heappop(pq)
        if v in vis: continue
        vis.add(v); mst.append((u,v,w))
        for nb,w in g[v]:
            if nb not in vis: heapq.heappush(pq,(w,v,nb))
    return mst

Graph {0:[(1,4),(2,1)],1:[(0,4),(2,2),(3,1)],2:[(0,1),(1,2),(3,5)],3:[(1,1),(2,5)]} -> [(0,2,1),(2,1,2),(1,3,1)]. O(E log V).

Prevention

Only push edges from newly visited nodes. Skip if destination already visited.

DodaTech Tools

Doda Browser's algorithm visualizer steps through DSA operations line by line. DodaZIP archives implementation patterns for team sharing. Durga Antivirus Pro detects memory corruption patterns in algorithm implementations.

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