[Joo kangsan] 24.11.19

[JooKangsan]

📌 푼 문제

문제이름	문제링크
Binary Tree Level Order Traversal	https://leetcode.com/problems/binary-tree-level-order-traversal
Subtree Of Another Tree	https://leetcode.com/problems/subtree-of-another-tree
House Robber II	https://leetcode.com/problems/house-robber-ii
Evaluate Reverse Polish Notation	https://leetcode.com/problems/evaluate-reverse-polish-notation

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📝 간단한 풀이 과정

102. Binary Tree Level Order Traversal

var levelOrder = function(root) {
  if (!root) return [];
  
  const result = [];
  const queue = [root];
  
  while (queue.length > 0) {
      const levelSize = queue.length;
      const currentLevel = [];
      
      for (let i = 0; i < levelSize; i++) {
          const node = queue.shift();
          currentLevel.push(node.val);
          
          if (node.left) queue.push(node.left);
          if (node.right) queue.push(node.right);
      }
      
      result.push(currentLevel);
  }
  
  return result;
};

572. Subtree Of Another Tree

var isSubtree = function(root, subRoot) {
  if (!subRoot) return true;
  if (!root) return false;
  
  const isSameTree = (tree1, tree2) => {
      if (!tree1 && !tree2) return true;
      if (!tree1 || !tree2) return false;
      if (tree1.val !== tree2.val) return false;
      return isSameTree(tree1.left, tree2.left) && 
             isSameTree(tree1.right, tree2.right);
  };
  
  return isSameTree(root, subRoot) || 
         isSubtree(root.left, subRoot) || 
         isSubtree(root.right, subRoot);
};

213. House Robber II

기존에 풀었던 House Robber 로직을 사용해서 풀었습니다.

var rob = function (nums) {
  let n = nums.length;
  if (n === 0) return 0;
  if (n === 1) return nums[0];
  if (n === 2) return Math.max(nums[0], nums[1]);

  let firstCase = [...nums];
  firstCase.pop();
  let first = robHelper(firstCase);

  let secondCase = [...nums];
  secondCase.shift();
  let second = robHelper(secondCase);

  return Math.max(first, second);
};

function robHelper(houses) {
  let n = houses.length;
  let dp = new Array(n).fill(0);
  dp[0] = houses[0];
  dp[1] = Math.max(houses[0], houses[1]);

  for (let i = 2; i < n; i++) {
    dp[i] = Math.max(dp[i - 1], dp[i - 2] + houses[i]);
  }
  return dp[n - 1];
}

207. Course Schedule

여기는 아직 문재의 해결 방법을 이해하고 풀지를 못해서 풀지못했습니다...ㅠ 다음 주에 작성해서 올리겠습니다

150. Evaluate Reverse Polish Notation

include 를 통해서 연산자를 찾고 연산자의 앞두개를 연산자로 처리한뒤 다시 그자리에 넣어줬습니다.

var evalRPN = function (tokens) {
  while (tokens.length > 1) {
    for (let i = 0; i < tokens.length; i++) {
      if (["+", "-", "*", "/"].includes(tokens[i])) {
        const num1 = Number(tokens[i - 2]);
        const num2 = Number(tokens[i - 1]);
        const operator = tokens[i];
        let result;

        switch (operator) {
          case "+":
            result = num1 + num2;
            break;
          case "-":
            result = num1 - num2;
            break;
          case "*":
            result = num1 * num2;
            break;
          case "/":
            result =
              num1 / num2 > 0
                ? Math.floor(num1 / num2)
                : Math.ceil(num1 / num2);
            break;
        }

        tokens.splice(i - 2, 3, result.toString());
        break;
      }
    }
  }
  return Number(tokens[0]);
};