diff --git a/code_study/Baekjoon/c/30805.c b/code_study/Baekjoon/c/30805.c
new file mode 100644
index 0000000..f18a768
--- /dev/null
+++ b/code_study/Baekjoon/c/30805.c
@@ -0,0 +1,75 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct {
+    int index, value;
+} Pair;
+
+int comparator(const void* a, const void* b) {
+    Pair* A = (Pair*)a;
+    Pair* B = (Pair*)b;
+
+    if(A->value == B->value) return A->index - B->index;
+    return B->value - A->value;
+}
+
+int main() {
+    int N;
+    scanf("%d",&N);
+    Pair* pair_A = (Pair*)malloc(sizeof(Pair)*N);
+
+    for(int i=0; i<N; i++) {
+        int value;
+        scanf("%d",&value);
+        Pair temp = {i, value};
+        pair_A[i] = temp;
+    }
+
+    qsort(pair_A, N, sizeof(Pair),comparator);
+
+    int M;
+    scanf("%d",&M);
+    Pair* pair_B = (Pair*)malloc(sizeof(Pair)*M);
+
+    for(int i=0; i<M; i++) {
+        int value;
+        scanf("%d",&value);
+        Pair temp = {i, value};
+        pair_B[i] = temp;
+    }
+
+    qsort(pair_B, M, sizeof(Pair), comparator);
+
+    int idxA = 0, idxB = 0;
+    int limitA = -1, limitB = -1;
+    int* subsequence = (int*)malloc(sizeof(int)*(M > N ? M : N));
+    int size = 0;
+
+    while(idxA < N && idxB < M) {
+        int posA = pair_A[idxA].index, valA = pair_A[idxA].value;
+        int posB = pair_B[idxB].index, valB = pair_B[idxB].value;
+
+        if(valA == valB) {
+            if(posA > limitA && posB > limitB) {
+                subsequence[size++] = valA;
+                idxA++; idxB++;
+                limitA = posA;
+                limitB = posB;
+            }
+            else if(posA <= limitA) idxA++;
+            else idxB++;
+        }
+        else if(valA > valB) idxA++;
+        else idxB++;
+    }
+
+    printf("%d\n",size);
+    for(int i=0; i<size; i++) printf("%d ",subsequence[i]);
+    printf("\n");
+
+    free(pair_A);
+    free(pair_B);
+    free(subsequence);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/code_study/Baekjoon/java/_1238.java b/code_study/Baekjoon/java/_1238.java
new file mode 100644
index 0000000..aa05fca
--- /dev/null
+++ b/code_study/Baekjoon/java/_1238.java
@@ -0,0 +1,92 @@
+import java.util.*;
+
+class Tuple implements Comparable<Tuple>{
+    int now,time;
+
+    Tuple(int now, int time) {
+        this.now = now;
+        this.time = time;
+    }
+
+    @Override
+    public int compareTo(Tuple other) {
+        return Integer.compare(this.time, other.time);
+    }
+}
+
+public class _1238 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        int N = sc.nextInt();
+        int M = sc.nextInt();
+        int X = sc.nextInt();
+
+        @SuppressWarnings("unchecked")
+        ArrayList<Tuple>[] graph = new ArrayList[N+1];
+
+        @SuppressWarnings("unchecked")
+        ArrayList<Tuple>[] reverse_graph = new ArrayList[N+1];
+        for(int i=0; i<=N; i++) {
+            graph[i] = new ArrayList<Tuple>();
+            reverse_graph[i] = new ArrayList<Tuple>();
+        }
+
+        for(int i=0; i<M; i++) {
+            int u = sc.nextInt();
+            int v = sc.nextInt();
+            int t = sc.nextInt();
+
+            graph[u].add(new Tuple(v,t));
+            reverse_graph[v].add(new Tuple(u, t));
+        }
+
+        sc.close();
+
+        PriorityQueue<Tuple> pq = new PriorityQueue<>();
+
+        // X -> N
+        pq.add(new Tuple(X, 0));
+        int[] coming_time = new int[N+1];
+        Arrays.fill(coming_time, Integer.MAX_VALUE);
+        coming_time[X] = 0;
+
+        while(!pq.isEmpty()) {
+            Tuple current = pq.poll();
+
+            if(current.time > coming_time[current.now]) continue;
+
+            for (Tuple next : graph[current.now]) {
+                if(coming_time[next.now] > current.time + next.time) {
+                    coming_time[next.now] = current.time + next.time;
+                    pq.add(new Tuple(next.now, coming_time[next.now]));
+                }
+            }
+        }
+
+        // N -> X
+        pq.add(new Tuple(X, 0));
+        int[] going_time = new int[N+1];
+        Arrays.fill(going_time, Integer.MAX_VALUE);
+        going_time[X] = 0;
+
+        while(!pq.isEmpty()) {
+            Tuple current = pq.poll();
+
+            if(current.time > going_time[current.now]) continue;
+
+            for (Tuple next : reverse_graph[current.now]) {
+                if(going_time[next.now] > current.time + next.time) {
+                    going_time[next.now] = current.time + next.time;
+                    pq.add(new Tuple(next.now, going_time[next.now]));
+                }
+            }
+        }
+
+        int maxTime = 0;
+        for(int i=1; i<=N; i++) {
+            maxTime = Math.max(maxTime, going_time[i] + coming_time[i]);
+        }
+
+        System.out.println(maxTime);
+    }
+}