1. Prim演算法（卡碼網 53）
# 最小生成樹prim演算法
# 貪心地選擇距離已有集合最小的邊加入
def prim(graph) -> int:
result = 0
visited = [False for _ in range(len(graph))]
# 未選點距離已選集合的最短距離
minDist = [10001 for _ in range(len(graph))]
# 初始化：加入節點1
visited[1] = True
for i in range(2, len(minDist)):
minDist[i] = graph[1][i]
# 還要加入n-1個頂點
for i in range(len(minDist)-2):
node_to_add = -1
minVal = 10001
for j in range(2, len(minDist)):
if visited[j] == False and minDist[j] < minVal:
minVal = minDist[j]
node_to_add = j
# 將最近的未訪問的節點加入集合
visited[node_to_add] = True
result += minVal
# 更新minDist陣列
for j in range(2, len(minDist)):
if visited[j] == False and graph[node_to_add][j] < minDist[j]:
minDist[j] = graph[node_to_add][j]
return result
def main():
num_node, num_edge = map(int, input().split())
graph = [[10001 for _ in range(num_node+1)] for _ in range(num_node+1)]
for _ in range(num_edge):
node1, node2, val = map(int, input().split())
graph[node1][node2] = val
graph[node2][node1] = val
print(prim(graph))
if __name__ == "__main__":
main()