What is the implementation method of recursive algorithm in JavaScript

Recursive algorithm is a common algorithm idea. Through the call of recursive functions, the problem can be decomposed and solved. In JavaScript, the implementation of recursive functions is very simple. You only need to pay attention to the order of function calls and exit conditions.

Next, we will introduce the implementation method of recursive algorithm in JavaScript through examples.

Example 1: Find the value of the nth term of the Fibonacci sequence

The Fibonacci sequence refers to: 0, 1, 1, 2, 3, 5, 8, 13 , 21, 34, ..., that is, the first item is 0, the second item is 1, and each subsequent item is the sum of the previous two items. The following uses a recursive algorithm to find the value of the nth item of the Fibonacci sequence:

function fibonacci(n) {
  if(n <= 1) {
    return n;
  } else {
    return fibonacci(n-1) + fibonacci(n-2);
  }
}

In the above code, first determine whether n is 1 or 0. If so, return n itself as the exit of the recursion. condition. If n is not 1 or 0, decompose the problem into solving the sum of the first two items, and call its own function recursively until the exit condition is reached.

Example 2: Tower of Hanoi problem

The Tower of Hanoi problem is a classic recursive problem. The problem is described as follows: There are three pillars, and a number of sizes are placed on one of them. Among the different disks, the bottom disk is the largest, and the other disks decrease in order. Now you need to move these discs to another pillar. During the movement, you must place the smaller disc on one pillar on top of the larger disc, and only one disc can be moved at a time. I would like to ask, when the moving conditions are met, how many moves are needed to move all the disks to another pillar?

The following is the implementation of the recursive algorithm for the Tower of Hanoi problem:

function hannuo(n, A, B, C) {
  if(n === 1) {
    console.log(`将第${n}个圆盘从${A}移动到${C}`);
  } else {
    hannuo(n-1, A, C, B);
    console.log(`将第${n}个圆盘从${A}移动到${C}`);
    hannuo(n-1, B, A, C);
  }
}

Among them, n represents the number of disks, A, B, and C represent three pillars respectively. The function of the recursive function hannuo is to n disks are moved from the bottom of A to the bottom of C, and the bottom of B needs to be used in the middle. During the recursive process, it is necessary to continuously solve the smaller sub-problems until the recursion reaches the smallest problem: moving the first disk from A to the bottom of C. C. The final result is to call hannuo(n, 'A', 'B', 'C') to solve and output the moving steps.

Recursive algorithms can help us solve some complex problems, but we also need to be careful to avoid infinite recursion, so we must be careful when writing code.

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