김승우 4주차 과제 구현

problem-1/SymbolTableWithArray.js

@@ -1,4 +1,95 @@
+class Node {
+  key;
+
+  item;
+
+  constructor(key, item) {
+    this.key = key;
+    this.item = item;
+  }
+}
+
 class SymbolTable {
+  #items = [];
+
+  #n = 0;
+
+  size() {
+    return this.#n;
+  }
+
+  isEmpty() {
+    return this.size() === 0;
+  }
+
+  #findIndex(key) {
+    return this.#items.findIndex((item) => item.key === key);
+  }
+
+  get(key) {
+    const node = this.#items.find((item) => item.key === key);
+
+    return node?.item;
+  }
+
+  put(key, item) {
+    const curIndex = this.#findIndex(key);
+
+    if (curIndex >= 0) {
+      this.#items[curIndex].item = item;
+
+      return;
+    }
+
+    const node = new Node(key, item);
+
+    this.#items[this.#n] = node;
+
+    this.#n += 1;
+  }
+
+  delete(key) {
+    const index = this.#findIndex(key);
+
+    if (index < 0) {
+      return;
+    }
+
+    this.#items.splice(index, 1);
+
+    this.#n -= 1;
+  }
+
+  contains(key) {
+    return !!this.get(key);
+  }
+
+  values() {
+    return this.#items.map(({ item }) => item);
+  }
+
+  keys() {
+    const data = [...this.#items];
+    let index = 0;
+
+    return {
+      [Symbol.iterator]() {
+        return {
+          next() {
+            if (index >= data.length) {
+              return { done: true };
+            }
+
+            const { key } = data[index];
+
+            index += 1;
+
+            return { done: false, value: key };
+          },
+        };
+      },
+    };
+  }
 }
 
 module.exports = {

problem-1/problem-1.test.js

@@ -124,3 +124,19 @@ test('심볼 테이블은 키에 해당하는 값을 저장한다', () => {
   expect(st.get('something')).toBeUndefined();
   expect(st.get('this')).toBeUndefined();
 });
+
+test('키를 순회할 수 있다', () => {
+  const st = new SymbolTable();
+
+  st.put('foo', 'bar');
+  st.put('something', 'that');
+  st.put('this', 'is');
+
+  const keys = [];
+
+  for (const key of st.keys()) {
+    keys.push(key);
+  }
+
+  expect(keys).toEqual(['foo', 'something', 'this']);
+});

problem-2/SymbolTable.js

@@ -63,18 +63,28 @@ class SymbolTable {
     this.#n--;
   }
 
-  rank(key, start = 0, end = this.#n - 1) {
-    if (start > end) {
-      return start;
+  rank(key) {
+    let mid = 0;
+    let start = 0;
+    let end = this.#n - 1;
+
+    while (start <= end) {
+      // 가운데 인덱스
+      mid = Math.floor((start + end) / 2);
+
+      if (this.#keys[mid] === key) {
+        return mid;
+      }
+
+      // 대소 비교로 범위 지정
+      if (this.#keys[mid] > key) {
+        end = mid - 1;
+      } else {
+        start = mid + 1;
+      }
     }
 
-    const mid = start + Math.floor((end - start) / 2);
-    if (key < this.#keys[mid]) {
-      return this.rank(key, start, mid - 1);
-    } if (key > this.#keys[mid]) {
-      return this.rank(key, mid + 1, end);
-    }
-    return mid;
+    return start;
   }
 
   min() {
@@ -106,15 +116,54 @@ class SymbolTable {
   }
 
   contains(key) {
+    const i = this.rank(key);
+
+    if (key === this.#keys[i] && i < this.#n) {
+      return true;
+    }
+
+    return false;
   }
 
   floor(key) {
+    const i = this.rank(key);
+
+    if (key === this.#keys[i]) {
+      return key;
+    }
+
+    if (i === 0) {
+      return;
+    }
+
+    return this.#keys[i - 1];
   }
 
   ceiling(key) {
+    const i = this.rank(key);
+
+    if (i >= this.#n) {
+      return;
+    }
+
+    return this.#keys[i];
   }
 
   keysRange(start, end) {
+    const i = this.rank(this.ceiling(start));
+    const j = this.rank(this.floor(end));
+
+    if (i > j || i < 0 || j >= this.#n) {
+      return [];
+    }
+
+    const keys = [];
+
+    for (let k = i; k <= j; k++) {
+      keys.push(this.#keys[k]);
+    }
+
+    return keys;
   }
 }
 

problem-3/SymbolTable.js

@@ -9,10 +9,13 @@ class Node {
 
   n;
 
-  constructor(key, value, n) {
+  h;
+
+  constructor(key, value, n, h = 0) {
     this.key = key;
     this.value = value;
     this.n = n;
+    this.h = h;
   }
 }
 
@@ -23,10 +26,12 @@ class SymbolTable {
     return this.#root === undefined;
   }
 
+  // 테이블의 사이즈 반환 = 모든 노드의 개수
   size() {
     return this.#size(this.#root);
   }
 
+  // eslint-disable-next-line class-methods-use-this
   #size(node) {
     if (node === undefined) {
       return 0;
@@ -58,7 +63,7 @@ class SymbolTable {
 
   #put(node, key, value) {
     if (node === undefined) {
-      return new Node(key, value, 1);
+      return new Node(key, value, 1, 0);
     }
 
     if (key < node.key) {
@@ -69,7 +74,8 @@ class SymbolTable {
       node.value = value;
     }
 
-    node.n = this.#size(node.left) + this.#size(node.right) + 1;
+    node.n = 1 + this.#size(node.left) + this.#size(node.right);
+    node.h = 1 + Math.max(this.#height(node.left), this.#height(node.right));
     return node;
   }
 
@@ -160,9 +166,12 @@ class SymbolTable {
 
     if (key < node.key) {
       return this.#rank(node.left, key);
-    } if (key > node.key) {
+    }
+
+    if (key > node.key) {
       return 1 + this.#size(node.left) + this.#rank(node.right, key);
     }
+
     return this.#size(node.left);
   }
 
@@ -212,7 +221,8 @@ class SymbolTable {
       node.left = t.left;
     }
 
-    node.n = this.#size(node.left) + this.#size(node.right) + 1;
+    node.n = 1 + this.#size(node.left) + this.#size(node.right);
+    node.h = 1 + Math.max(this.#height(node.left), this.#height(node.right));
     return node;
   }
 
@@ -269,6 +279,45 @@ class SymbolTable {
 
     return this.#max(node.right);
   }
+
+  height() {
+    if (this.isEmpty()) {
+      return -1;
+    }
+
+    return this.#height(this.#root);
+  }
+
+  // 재귀적인 방법으로 트리의 높이 구하기 1
+  // #height(node, h = 0) {
+  //   if (node === undefined) {
+  //     return h - 1;
+  //   }
+
+  //   return Math.max(this.#height(node.left, 1 + h), this.#height(node.right, 1 + h));
+  // }
+
+  // 재귀적인 방법으로 트리의 높이 구하기 2
+  // #height(node) {
+  //   if (!node) {
+  //     return 0;
+  //   }
+
+  //   if (!node.left && !node.right) {
+  //     return 0;
+  //   }
+
+  //   return 1 + Math.max(this.#height(node.left), this.#height(node.right));
+  // }
+
+  // eslint-disable-next-line class-methods-use-this
+  #height(node) {
+    if (node === undefined) {
+      return -1;
+    }
+
+    return node.h;
+  }
 }
 
 module.exports = {