JavaScript函数：高效查找数组中的最大值与最小值

function findBiggestAndSmallest(numbers) {
  let obj = {};
  obj.biggest = Math.max(...numbers);
  obj.smallest = Math.min(...numbers);
  return obj;
}

console.log(findBiggestAndSmallest([5, 2, 9, 7])); // { biggest: 9, smallest: 2 }

console.log(findBiggestAndSmallest([])); // { biggest: -Infinity, smallest: Infinity }
// 期望结果是 {}

/**
 * 查找数组中的最大值和最小值，并以对象形式返回。
 * 处理空数组、单元素数组及无效输入等边界情况。
 * @param {number[]} numbers - 数字数组。
 * @returns {{biggest: number, smallest: number}|{}|null} 包含最大值和最小值的对象，
 *          或空对象（数组为空时），或null（输入无效时）。
 */
function findBiggestAndSmallest(numbers) {
  // 1. 处理无效输入：如果numbers为null或undefined
  if (numbers === null || numbers === undefined) {
    return null;
  }

  // 2. 处理空数组
  if (numbers.length === 0) {
    return {};
  }

  // 3. 处理单元素数组
  if (numbers.length === 1) {
    const [first] = numbers; // 使用解构赋值获取第一个元素
    return { biggest: first, smallest: first }; // 使用对象字面量语法
  }

  // 4. 处理多元素数组
  return {
    biggest: Math.max(...numbers),
    smallest: Math.min(...numbers)
  };
}

// 测试用例
const areEqual = (a, b) => JSON.stringify(a) === JSON.stringify(b); // 辅助函数用于深度比较对象

console.log('--- 解决方案一测试 ---');
console.log(`findBiggestAndSmallest(null): ${JSON.stringify(findBiggestAndSmallest(null))} (Expected: null)`);
console.log(`findBiggestAndSmallest(undefined): ${JSON.stringify(findBiggestAndSmallest(undefined))} (Expected: null)`);
console.log(`findBiggestAndSmallest([]): ${JSON.stringify(findBiggestAndSmallest([]))} (Expected: {})`);
console.log(`findBiggestAndSmallest([5]): ${JSON.stringify(findBiggestAndSmallest([5]))} (Expected: {biggest:5,smallest:5})`);
console.log(`findBiggestAndSmallest([5, 2, 9, 7]): ${JSON.stringify(findBiggestAndSmallest([5, 2, 9, 7]))} (Expected: {biggest:9,smallest:2})`);

// 验证结果
console.log(`null input test: ${areEqual(null, findBiggestAndSmallest(null))}`);
console.log(`empty array test: ${areEqual({}, findBiggestAndSmallest([]))}`);
console.log(`single element array test: ${areEqual({biggest:5,smallest:5}, findBiggestAndSmallest([5]))}`);
console.log(`multiple elements array test: ${areEqual({biggest:9,smallest:2}, findBiggestAndSmallest([5, 2, 9, 7]))}`);

/**
 * 查找数组中的最大值和最小值，使用reduce方法实现单次遍历。
 * 处理空数组、单元素数组及无效输入等边界情况。
 * @param {number[]} numbers - 数字数组。
 * @returns {{biggest: number, smallest: number}|{}|null} 包含最大值和最小值的对象，
 *          或空对象（数组为空时），或null（输入无效时）。
 */
function findBiggestAndSmallestOptimized(numbers) {
  // 1. 处理无效输入
  if (numbers === null || numbers === undefined) {
    return null;
  }

  // 2. 处理空数组
  if (numbers.length === 0) {
    return {};
  }

  // 3. 处理单元素数组 (reduce 也可以处理，但为了清晰和性能，这里单独处理)
  if (numbers.length === 1) {
    const [first] = numbers;
    return { biggest: first, smallest: first };
  }

  // 4. 使用 reduce 方法进行单次遍历
  // 初始值可以设置为数组的第一个元素，或者使用极值
  // 这里我们使用极值作为初始值，确保无论数组元素正负都能正确比较
  return numbers.reduce((result, n) => {
    if (n < result.smallest) {
      result.smallest = n;
    }
    if (n > result.biggest) {
      result.biggest = n;
    }
    return result;
  }, {
    biggest: -Number.MAX_VALUE, // 初始最大值设置为尽可能小的数
    smallest: Number.MAX_VALUE  // 初始最小值设置为尽可能大的数
  });
}

// 测试用例
console.log('\n--- 解决方案二测试 (优化版) ---');
console.log(`findBiggestAndSmallestOptimized(null): ${JSON.stringify(findBiggestAndSmallestOptimized(null))} (Expected: null)`);
console.log(`findBiggestAndSmallestOptimized(undefined): ${JSON.stringify(findBiggestAndSmallestOptimized(undefined))} (Expected: null)`);
console.log(`findBiggestAndSmallestOptimized([]): ${JSON.stringify(findBiggestAndBiggestOptimized([]))} (Expected: {})`);
console.log(`findBiggestAndSmallestOptimized([5]): ${JSON.stringify(findBiggestAndSmallestOptimized([5]))} (Expected: {biggest:5,smallest:5})`);
console.log(`findBiggestAndSmallestOptimized([5, 2, 9, 7]): ${JSON.stringify(findBiggestAndSmallestOptimized([5, 2, 9, 7]))} (Expected: {biggest:9,smallest:2})`);

// 验证结果
console.log(`null input test (optimized): ${areEqual(null, findBiggestAndSmallestOptimized(null))}`);
console.log(`empty array test (optimized): ${areEqual({}, findBiggestAndSmallestOptimized([]))}`);
console.log(`single element array test (optimized): ${areEqual({biggest:5,smallest:5}, findBiggestAndSmallestOptimized([5]))}`);
console.log(`multiple elements array test (optimized): ${areEqual({biggest:9,smallest:2}, findBiggestAndSmallestOptimized([5, 2, 9, 7]))}`);