Merge pull request #264 from AlgoLeadMe/85-tgyuuAn

85-tgyuuAn

tgyuuAn/README.md

@@ -86,5 +86,6 @@
 | 82차시 | 2024.11.22 |  희소 배열  | <a href="https://www.acmicpc.net/problem/17435">합성함수와 쿼리</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/257
 | 83차시 | 2024.12.01 |  수학 + 구현 | <a href="https://www.acmicpc.net/problem/1033">칵테일</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/259
 | 84차시 | 2024.12.31 |  BFS | <a href="https://www.acmicpc.net/problem/4179">불!</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/261
+| 85차시 | 2025.01.09 |  다익스트라 + 이분 탐색 | <a href="https://www.acmicpc.net/problem/1800">인터넷 설치</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/264
 | 86차시 | 2025.01.16 |  이분 탐색  | <a href="https://www.acmicpc.net/problem/1114">통나무 자르기</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/265
 ---

tgyuuAn/다익스트라/인터넷 설치.py

@@ -0,0 +1,66 @@
+import sys
+from heapq import *
+
+def input(): return sys.stdin.readline().rstrip()
+
+N, P, K = map(int, input().split())
+graph = [[int(1e9) for _ in range(N+1)] for _ in range(N+1)]
+
+for _ in range(P):
+    start, destination, cost = map(int, input().split())
+    graph[start][destination] = min(graph[start][destination], cost)
+    graph[destination][start] = min(graph[destination][start], cost)
+
+def check(mid):
+    if dijkstra(mid): return True
+    return False
+
+def dijkstra(_max):
+    visited = set()
+    DP = [[int(1e9) for _ in range(K+1)] for _ in range(N+1)]
+    DP[1][K] = 0
+
+    # 간선 코스트, 남은 기회, 현재 노드
+    heap = [(0, K, 1)]
+    while heap:
+        now_cost, now_remain, now_node = heappop(heap)
+
+        if (now_node, now_remain) in visited: continue
+        visited.add((now_node, now_remain))
+
+        if DP[now_node][now_remain] < now_cost: continue
+        DP[now_node][now_remain] = now_cost
+
+        if now_node == N:
+            return True
+
+        for idx, cost in enumerate(graph[now_node]):
+            if idx == 0: continue
+            if cost == int(1e9): continue
+
+            if cost <= _max:
+                if (idx, now_remain) in visited: continue
+                if DP[idx][now_remain] > cost: heappush(heap, (cost, now_remain, idx))
+
+            elif cost > _max and now_remain >= 1: 
+                if (idx, now_remain-1) in visited: continue
+                if DP[idx][now_remain-1] > cost: heappush(heap, (cost, now_remain-1, idx))    
+
+    for idx in range(1, K+1):
+        if DP[N][idx] != int(1e9): return True
+
+    return False
+
+answer = int(1e9)
+left = -1
+right = 1_000_001 
+while left+1<right:
+    mid = (left + right) // 2
+
+    if check(mid): 
+        right = mid
+        answer = mid
+    else: left = mid
+
+if answer != int(1e9): print(answer)
+else: print(-1)