diff --git a/code_study/Baekjoon/c/10845.c b/code_study/Baekjoon/c/10845.c
new file mode 100644
index 0000000..5b0952a
--- /dev/null
+++ b/code_study/Baekjoon/c/10845.c
@@ -0,0 +1,65 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int opcodeToNum(char* opcode);
+
+int main() {
+    int N;
+    scanf("%d\n",&N);
+    int queue[10000];
+    int front = 0, rear = 0, size = 0;
+
+    while(N--){
+        char opcode[6];
+        int operend;
+        scanf("%s",opcode);
+
+        switch(opcodeToNum(opcode))
+        {
+            case 0:
+            {
+                scanf("%d\n",&operend);
+                queue[rear++] = operend;
+                size++;
+                break;
+            }
+            case 1:
+            {
+                printf("%d\n", size ? queue[front++] : -1);
+                size = size ? size - 1 : 0;
+                break;
+            }
+            case 2:
+            {
+                printf("%d\n",size);
+                break;
+            }
+            case 3:
+            {
+                printf("%d\n", size ? 0 : 1);
+                break;
+            }
+            case 4:
+            {
+                printf("%d\n", size ? queue[front] : -1);
+                break;
+            }
+            case 5:
+            {
+                printf("%d\n", size ? queue[rear-1] : -1);
+            }
+        }
+    }
+    return 0;
+}
+
+int opcodeToNum(char* opcode){
+    if(!strcmp(opcode, "push")) return 0;
+    else if(!strcmp(opcode, "pop")) return 1;
+    else if(!strcmp(opcode, "size")) return 2;
+    else if(!strcmp(opcode, "empty")) return 3;
+    else if(!strcmp(opcode, "front")) return 4;
+    else if(!strcmp(opcode, "back")) return 5;
+    return -1;
+}
diff --git a/code_study/Baekjoon/c/11866.c b/code_study/Baekjoon/c/11866.c
new file mode 100644
index 0000000..b854c37
--- /dev/null
+++ b/code_study/Baekjoon/c/11866.c
@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int nextIndex(int current_idx, int* arr, int n, int k);
+
+int main() {
+    int n, k;
+    scanf("%d %d",&n, &k);
+    int* list = (int*)malloc(sizeof(int)*(n+1));
+    for(int i=0; i<=n; i++) {
+        list[i] = i;
+    }
+
+    printf("<");
+    int len = n, current_idx=1;
+    while(len!=0) {
+        current_idx = nextIndex(current_idx, list, n, len==n ? k-1 : k);
+        if(len==1) printf("%d>\n", list[current_idx]);
+        else printf("%d, ",list[current_idx]);
+        list[current_idx] = 0;
+        len--;
+    }
+    free(list);
+    return 0;
+}
+
+int nextIndex(int current_idx, int* arr, int n, int k){
+    while(k--){
+        do{
+            if(current_idx==n) current_idx = 1;
+            else current_idx++;
+        }while(arr[current_idx]==0);
+    }
+    return current_idx;
+}