diff --git a/@sammo/util/src/index.ts b/@sammo/util/src/index.ts
index 2c2c730..2cdef73 100644
--- a/@sammo/util/src/index.ts
+++ b/@sammo/util/src/index.ts
@@ -6,6 +6,7 @@ export * from "./must.js"
 export * from "./types.js"
 export * from "./web.js"
 export * from "./signal.js"
+export * from "./sorted.js"
 
 export * from "./strongType.js"
 
diff --git a/@sammo/util/src/sorted.ts b/@sammo/util/src/sorted.ts
new file mode 100644
index 0000000..2af433a
--- /dev/null
+++ b/@sammo/util/src/sorted.ts
@@ -0,0 +1,75 @@
+type IndexableRaw<T> = {
+    [key: number]: T;
+}
+type IndexableGet<T> = {
+    get(index: number): T | undefined;
+}
+
+type IndexableAt<T> = {
+    at(index: number): T;
+}
+
+interface BasicResizableArrayLike<T> {
+    length: number;
+    splice(start: number, deleteCount: number, ...items: T[]): T[] | undefined;
+    shift(): T | undefined;
+    unshift(items: T): number;
+    push(items: T): number;
+    pop(): T | undefined;
+}
+
+export type ResizableArrayLike<T> = BasicResizableArrayLike<T> & (IndexableRaw<T> | IndexableGet<T> | IndexableAt<T>);
+/**
+ * 이미 정렬된 배열에 아이템 추가.
+ * Array와 Denque 지원.
+ *
+ * @param arr 정렬된 배열, splice, shift, unshift, push, pop과 at, get, []중 하나의 조회법 지원
+ * @param item 추가할 아이템
+ * @param compareFn 비교함수. 앞에 오는 경우 -1, 뒤에 오는 경우 1, 같은 경우 0을 반환해야 함.
+ * @param maybeTail false인 경우 binary search, true인 경우 뒤부터 순차 검색
+ *
+ * @returns
+ */
+export function insertItemAtArrayLike<T, Arr extends ResizableArrayLike<T>>(arr: Arr, item: T, compareFn: (a: T, b: T) => number, maybeTail = false): ResizableArrayLike<T> {
+    const getter: ((i: number) => T) = (() => {
+        if ('at' in arr) {
+            return (i: number) => arr.at(i)!;
+        }
+        if ('get' in arr) {
+            return (i: number) => arr.get(i)!;
+        }
+        return (i: number) => arr[i];
+    })();
+
+    if (arr.length === 0) {
+        arr.push(item);
+        return arr;
+    }
+
+    if (maybeTail) {
+        for (let i = arr.length - 1; i >= 0; i--) {
+            if (compareFn(getter(i), item) <= 0) {
+                arr.splice(i + 1, 0, item);
+                return arr;
+            }
+        }
+        //맨 앞이라고..? 대체 왜 maybeTail=true를 쓰는거지?
+        arr.unshift(item);
+        return arr;
+    }
+
+    //binary search and insert
+    let left = 0;
+    let right = arr.length;
+    while (left < right) {
+        const mid = (left + right) >> 1;
+        const cmp = compareFn(getter(mid), item);
+        if (cmp < 0) {
+            left = mid + 1;
+        } else {
+            right = mid;
+        }
+    }
+    arr.splice(left, 0, item);
+    return arr;
+}
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