斐波那契数列<递归和排序>

算法（斐波那契数列两种方法分析)

  // 递归方法

  let data1 = new Date();
  function fib(n) {
      if (n === 1 || n === 2) return n - 1
      return fib(n - 1) + fib(n - 2)
  }
  let arr = []
  for (let index = 1; index < 10 ; index++) {
      arr.push(fib(index))
  }
  let data2 = new Date();

  console.log(arr, data2 - data1);


  //非递归方法 

  let data3 = new Date();

  function fib1(n) {
      if (n == 1) {
          return 0
      }
      let a = 0
      let b = 1
      let c = a + b
      for (let i = 3; i < n; i++) {
          a = b
          b = c
          c = a + b
      }
      return c
  }
  let arr1 = []
  for (let index = 1; index < 10; index++) {
      arr1.push(fib1(index))
  }
  let data4 = new Date();
  console.log(arr1, data4 - data3);

 递归优化存已经算过的值

var temp = []
var climbStairs = function(n) {
    if(n <= 0){
        return 0
    }
    if(n <= 2){
        return n
    }
    if(temp[n]){
        return temp[n]
    }
    temp[n] = climbStairs(n-2) + climbStairs(n-1)
    return temp[n]
};
console.log(climbStairs(10));