From 9de3692256577120e098be3a08c2e8a571842862 Mon Sep 17 00:00:00 2001
From: songyc macbook <gitea@gitea>
Date: Fri, 17 Oct 2025 23:35:52 +0900
Subject: [PATCH] 20251017 baekjoon

---
 code_study/Baekjoon/c/1865.c         | 74 +++++++++++++++++++++++
 code_study/Baekjoon/c/2638.c         | 88 ++++++++++++++++++++++++++++
 code_study/Baekjoon/swift/2440.swift |  8 +++
 3 files changed, 170 insertions(+)
 create mode 100644 code_study/Baekjoon/c/1865.c
 create mode 100644 code_study/Baekjoon/c/2638.c
 create mode 100644 code_study/Baekjoon/swift/2440.swift

diff --git a/code_study/Baekjoon/c/1865.c b/code_study/Baekjoon/c/1865.c
new file mode 100644
index 0000000..313d1c2
--- /dev/null
+++ b/code_study/Baekjoon/c/1865.c
@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+#define MAX_SIZE 5200
+#define MAX_NODE 501
+
+typedef struct {
+    int start;
+    int end;
+    int time;
+} Edge;
+
+int main() {
+    int T;
+    scanf("%d", &T);
+
+    Edge* edge = (Edge*)malloc(sizeof(Edge)*MAX_SIZE);
+    int* distance = (int*)malloc(sizeof(int)*MAX_NODE);
+
+    while(T--) {
+        int N, M, W;
+        scanf("%d %d %d",&N, &M, &W);
+        
+        // ROAD
+        for(int i=0; i<2*M; i+=2) {
+            int S, E, T;
+            scanf("%d %d %d",&S, &E, &T);
+
+            Edge temp1 = {S, E, T};
+            Edge temp2 = {E, S, T};
+
+            edge[i] = temp1;
+            edge[i+1] = temp2;
+        }
+
+        // WORM HOLE
+        for(int i=0; i<W; i++) {
+            int S, E, T;
+            scanf("%d %d %d",&S, &E, &T);
+
+            Edge temp = {S, E, T*(-1)};
+
+            edge[2*M+i] = temp;
+        }
+
+        memset(distance, 0, sizeof(int)*MAX_NODE);
+        bool negative_cycle = false;
+
+        for(int n=0; n<N; n++) {
+            for(int i=0; i<2*M+W; i++) {
+                int s = edge[i].start;
+                int e = edge[i].end;
+                int t = edge[i].time;
+
+                if(distance[e] > distance[s] + t) {
+                    distance[e] = distance[s] + t;
+
+                    if(n==N-1) {
+                        negative_cycle = true;
+                        break;
+                    }
+                }
+            }
+        }
+        
+        printf("%s\n", negative_cycle ? "YES" : "NO");
+    }
+
+    free(edge);
+    free(distance);
+    return 0;
+}
\ No newline at end of file
diff --git a/code_study/Baekjoon/c/2638.c b/code_study/Baekjoon/c/2638.c
new file mode 100644
index 0000000..7b1d9f8
--- /dev/null
+++ b/code_study/Baekjoon/c/2638.c
@@ -0,0 +1,88 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct {
+    int x;
+    int y;
+} Point;
+
+int main() {
+    int N, M;
+    scanf("%d %d", &N, &M);
+
+    int** paper = (int**)malloc(sizeof(int*)*N);
+    int cheese = 0;
+    int time = 0;
+
+    for(int i=0; i<N; i++) {
+        paper[i] = (int*)malloc(sizeof(int)*M);
+
+        for(int j=0; j<M; j++) {
+            scanf("%d",&paper[i][j]);
+
+            if(paper[i][j] == 1) cheese++;
+        }
+    }
+
+    int** visited = (int**)malloc(sizeof(int*)*N);
+    for(int i=0; i<N; i++) visited[i] = (int*)malloc(sizeof(int)*M);
+    Point* qu = (Point*)malloc(sizeof(Point)*(N*M));
+
+    while(cheese != 0) {
+        for(int i=0; i<N; i++) memset(visited[i], 0, sizeof(int)*M);
+
+        int q_front = 0;
+        int q_rear = 0;
+
+        Point start = {0,0};
+        qu[q_rear++] = start;
+        visited[0][0] = 1;
+
+        int dx[4] = {-1,1,0,0};
+        int dy[4] = {0,0,1,-1};
+
+        while(q_front != q_rear) {
+            Point now = qu[q_front++];
+
+            for(int i=0; i<4; i++) {
+                int nx = now.x + dx[i];
+                int ny = now.y + dy[i];
+
+                if(0<=nx && nx<M && 0<=ny && ny<N && paper[ny][nx] == 0 && visited[ny][nx] == 0) {
+                    Point next = {nx, ny};
+                    qu[q_rear++] = next;
+                    visited[ny][nx] = 1;
+
+                    for(int j=0; j<4; j++) {
+                        int nnx = next.x + dx[j];
+                        int nny = next.y + dy[j];
+
+                        if(0<=nnx && nnx<M && 0<=nny && nny<N && paper[nny][nnx] == 1) visited[nny][nnx]++; 
+                    }
+                }
+            }
+        }
+
+        for(int i=0; i<N; i++) {
+            for(int j=0; j<M; j++) {
+                if(paper[i][j] == 1 && visited[i][j] > 1) {
+                    paper[i][j] = 0;
+                    cheese--;
+                }
+            }
+        }
+
+        time++;
+    }
+
+    printf("%d\n",time);
+
+    for(int i=0; i<N; i++) free(paper[i]);
+    free(paper);
+    for(int i=0; i<N; i++) free(visited[i]);
+    free(visited);
+    free(qu);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/code_study/Baekjoon/swift/2440.swift b/code_study/Baekjoon/swift/2440.swift
new file mode 100644
index 0000000..4c50755
--- /dev/null
+++ b/code_study/Baekjoon/swift/2440.swift
@@ -0,0 +1,8 @@
+if let N = Int(readLine() ?? "") {
+    for n in 0..<N {
+        for _ in 0..<N-n {
+            print("*",terminator: "")
+        }
+        print()
+    }
+}
\ No newline at end of file