[Update] bfs예제 풀이

Author: rkdehdgns1230

Graph_searching_method/problem solving/[3055]_탈출.cpp

@@ -0,0 +1,126 @@
+#include <iostream>
+#include <queue>
+#include <string>
+
+#define MAX 51
+#define MAX_VAL 2501
+
+using namespace std;
+
+int r, c;
+int d, s;
+
+string map[MAX];
+int dp[MAX][MAX];
+
+queue<pair<int, int>> q;
+queue<pair<int, int>> waterQueue;
+
+void init() {
+	for (int i = 0; i < r; i++) {
+		for (int j = 0; j < c; j++) {
+			dp[i][j] = MAX_VAL;
+		}
+	}
+}
+
+bool inRange(int x, int y) {
+	return (0 <= x && x < r && 0 <= y && y < c);
+}
+
+void findMinPath() {
+	int dx[] = { -1, 1, 0, 0 };
+	int dy[] = { 0, 0, -1, 1 };
+	
+	while (!q.empty()) {
+		//현재 물이 범람한 칸만 탐색하기 위함이다.
+		int waterQueueSize = waterQueue.size();
+		for (int i = 0; i < waterQueueSize; i++) {
+
+			int currentWaterX = waterQueue.front().first;
+			int currentWaterY = waterQueue.front().second;
+			waterQueue.pop();
+
+			for (int j = 0; j < 4; j++) {
+				int nextWaterX = currentWaterX + dx[j];
+				int nextWaterY = currentWaterY + dy[j];
+
+				//범위 밖인지 확인한다.
+				if (!inRange(nextWaterX, nextWaterY))
+					continue;
+
+				if (map[nextWaterX][nextWaterY] == '.') {
+					//해당 칸은 물이 범람함
+					map[nextWaterX][nextWaterY] = '*';
+					waterQueue.push({ nextWaterX, nextWaterY });
+				}
+			}
+		}
+		int queueSize = q.size();
+
+		for (int i = 0; i < queueSize; i++) {
+			int x = q.front().first;
+			int y = q.front().second;
+			int dis = dp[x][y];
+			q.pop();
+
+			//도착지점이면 종료한다 (어차피 BFS)
+			if (map[x][y] == 'D') {
+				cout << dp[x][y];
+				return;
+			}
+
+			for (int j = 0; j < 4; j++) {
+				int nx = x + dx[j];
+				int ny = y + dy[j];
+				int nextDis = dis + 1;
+
+				if (!inRange(nx, ny) || (nextDis >= dp[nx][ny]))
+					continue;
+				//물이 범람한 지역이거나 출발 지점인 경우는 건너띈다. (돌 포함)
+				if (map[nx][ny] == '*' || map[nx][ny] == 'S' || map[nx][ny] == 'X')
+					continue;
+
+				//최단 시간 갱신하고, queue에 넣는다.
+				dp[nx][ny] = nextDis;
+				q.push({ nx, ny });
+			}
+		}
+	}
+
+	//결국 목적지에 도달하지 못한 경우에 해당한다.
+	cout << "KAKTUS";
+	return;
+}
+
+int main() {
+	ios::sync_with_stdio(false);
+	cin.tie(NULL);
+	cout.tie(NULL);
+
+	int desX, desY;
+
+	cin >> r >> c;
+
+	init();
+
+	for (int i = 0; i < r; i++) {
+		string row;
+		cin >> row;
+		map[i] = row;
+
+		for (int j = 0; j < c; j++) {
+			if (row[j] == '*') {
+				waterQueue.push({ i, j });
+			}
+			else if (row[j] == 'S') {
+				q.push({ i, j });
+				dp[i][j] = 0;
+			}
+		}
+	}
+
+	findMinPath();
+
+	return 0;
+}