Day3.2022.03.30

一、手写算法

https://leetcode-cn.com/problems/design-a-stack-with-increment-operation/

思路

• 实现栈的基础操作
• 创建栈结构：栈顶，存放栈数据，最大栈容量
• 实现入栈push，出栈pop，维护栈顶元素即可
• increment方法，判断循环次数，执行相加操作

  代码

  ```javascript /**
  • @param {number} maxSize */ var CustomStack = function(maxSize) { this.maxSize = maxSize; this.currentLength = 0; this.value = [] };

/**

• @param {number} x
• @return {void} */ CustomStack.prototype.push = function(x) { if(this.currentLength < this.maxSize){ this.value[this.currentLength] = x; this.currentLength++; } };

/**

• @return {number} */ CustomStack.prototype.pop = function() { if(this.currentLength > 0){ let val = this.value[this.currentLength - 1]; console.log(this.currentLength) this.currentLength—; return val; }else{ return -1 } };

/**

• @param {number} k
• @param {number} val
• @return {void} */ CustomStack.prototype.increment = function(k, val) { let len = k > this.currentLength ? this.currentLength :k for (let i = 0; i < len; i++) { this.value[i] = this.value[i] + val; } };

/**

• Your CustomStack object will be instantiated and called as such:
• var obj = new CustomStack(maxSize)
• obj.push(x)
• var param_2 = obj.pop()
• obj.increment(k,val) */ ```

  复杂度分析

• 时间复杂度：push，pop复杂度为O(1)，increment复杂度为O(n)
• 空间复杂度：O(n)

二、编程题

// 33. 实现`Promise.allSettled()`
// https://bigfrontend.dev/zh/problem/implement-Promise-allSettled

/**
 * @param {Array<any>} promises - notice that input might contains non-promises
 * @return {Promise<Array<{status: 'fulfilled', value: any} | {status: 'rejected', reason: any}>>}
 */
function allSettled(promises) {
  // your code here
  if (promises.length === 0) return Promise.resolve([]);
  let _promises = promises.map((item) =>
    item instanceof Promise ? item : Promise.resolve(item)
  );
  return new Promise((resolve, reject) => {
    let results = [];
    let count = _promises.length;
    _promises.forEach((promise, index) => {
      promise.then(
        (value) => {
          results[index] = {
            status: 'fulfilled',
            value: value,
          };
          count -= 1;
          if (count === 0) {
            resolve(results);
          }
        },
        (reason) => {
          results[index] = {
            status: 'rejected',
            reason: reason,
          };
          count -= 1;
          if (count === 0) {
            resolve(results);
          }
        }
      );
    });
  });
}