๐ ์ต๋จ ๊ฒฝ๋ก
- ๊ฐ์ฅ ์งง์ ๊ฒฝ๋ก๋ฅผ ์ฐพ๋ ์๊ณ ๋ฆฌ์ฆ์ผ๋ก ๊ทธ๋ํ๋ฅผ ์ด์ฉํด ํํ
๐ ๊ฐ๋จํ ๋ค์ต์คํธ๋ผ ์ต๋จ ๊ฒฝ๋ก์๊ณ ๋ฆฌ์ฆ
- ์ฌ๋ฌ๊ฐ์ ๋
ธ๋๊ฐ ์์ ๋, ํน์ ํ ๋
ธ๋์์ ์ถ๋ฐํ์ฌ ๋ค๋ฅธ ๋
ธ๋๋ก ๊ฐ๋ ๊ฐ๊ฐ์ ์ต๋จ ๊ฒฝ๋ก๋ฅผ ๊ตฌํด์ฃผ๋ ์๊ณ ๋ฆฌ์ฆ
- ๊ทธ๋ฆฌ๋ ์๊ณ ๋ฆฌ์ฆ
- ๋ค์ต์คํธ๋ผ ์๊ณ ๋ฆฌ์ฆ ์๊ฐ ๋ณต์ก๋ :
O(V^2)
import sys
input = sys.stdin.readline
INF = int(1e9)
n, m = map(int, input().split())
start = int(input())
graph = [[] for i in range(n+1)]
visited = [False]*(n+1)
distance = [INF]*(n+1)
for _ in range(m):
a, b, c = map(int, input().split())
graph[a].append((b,c))
def get_smallest_node():
min_value = INF
index = 0
for i in range(1, n+1):
if distance[i] < min_value and not visited[i]:
min_value = distance[i]
index = i
print(index)
return index
def dijkstra(start):
distance[start] = 0
visited[start] = True
for j in graph[start]:
distance[j[0]] = j[1]
for i in range(n-1):
now = get_smallest_node()
visited[now] = True
for j in graph[now]:
cost = distance[now] + j[1]
if cost < distance[j[0]]:
distance[j[0]] = cost
dijkstra(start)
for i in range(1, n+1):
if distance[i] == INF:
print("infinity")
else:
print(distance[i])
๐ ๊ฐ์ ๋ ๋ค์ต์คํธ๋ผ ์๊ณ ๋ฆฌ์ฆ
import heapq
import sys
input = sys.stdin.readline
INF = int(1e9)
# ๋
ธ๋ ๊ฐ์ ๊ฐ์, ์์ ๋
ธ๋ ์
๋ ฅ ๋ฐ๊ธฐ
n, m = map(int, input().split())
start = int(input())
graph = [[] for i in range(n+1)] # ๊ฐ ๋
ธ๋์ ์ฐ๊ฒฐ์ ๋ณด๊ฐ ๋ด๊ฒจ์๋ ๋ฆฌ์คํธ
distance = [INF]*(n+1) # ์ต๋จ ๊ฑฐ๋ฆฌ ํ
์ด๋ธ ๋ฌดํ์ผ๋ก ์ด๊ธฐํ
for _ in range(m):
a, b, c = map(int, input().split())
graph[a].append((b,c))
def dijkstra(start):
q = []
heapq.heappush([], (0, start))
distance[start] = 0
print(type(q))
while q:
dist, now = heapq.heappop(q)
if distance[now] < dist:
continue
for i in graph[now]:
cost = dist + i[1]
if cost < distance[i[0]]:
distance[i[0]] = cost
heapq.heappush(q, (cost, i[0]))
dijkstra(start)
for i in range(1, n+1):
if distance[i] == INF:
print("INF")
else:
print(distance)
๐ ํ๋ก์ด๋ ์์
์๊ณ ๋ฆฌ์ฆ
- ๋ชจ๋ ์ง์ ์์ ๋ค๋ฅธ ๋ชจ๋ ์ง์ ๊น์ง์ ์ต๋จ ๊ฒฝ๋ก๋ฅผ ๋ชจ๋ ๊ตฌํด์ผ ํ๋ ๊ฒฝ์ฐ
- DP ์๊ณ ๋ฆฌ์ฆ
- ํ๋ก์ด๋ ์์
์ ์๊ฐ ๋ณต์ก๋ :
O(N$^3$)
INF = int(1e9)
n = int(input())
m = int(input())
graph = [[INF] * (n+1) for _ in range(n+1)]
for i in range(1, n+1):
for j in range(1, n+1):
if i == j:
graph[i][j] = 0
for _ in range(m):
a, b, c = map(int, input().split())
graph[a][b] = c
for k in range(1, n+1):
for i in range(1, n+1):
for j in range(1, n+1):
graph[i][j] = min(graph[i][j], graph[i][k] + graph[k][j])
for i in range(1, n+1):
for j in range(1, n+1):
if graph[i][j] == INF:
print("INF")
else:
print(graph[i][j], end=' ')
print()