Recursive implementation of C++ functions: Application of recursion in programming competitions?

Recursion is a technique where a function calls itself to solve a problem, including a baseline condition to terminate the recursion. In C, you can use the return keyword to return a function value and terminate recursion. Recursion can be used to solve classic problems such as the Tower of Hanoi problem, where it moves n disks from one pole to another. In programming competitions, recursion is often used to solve tree-structured problems, depth-first search, backtracking, and divide and conquer.

Recursive implementation of C function: Application of recursion in programming competitions

What is recursion?

Recursion is a programming technique in which a function calls itself to solve a problem. A recursive function usually contains a baseline condition. When the baseline condition is reached, the function stops recursion and returns a result. Without a baseline condition, recursion will continue forever.

Implementation of recursion in C

In C, you can use the keyword return to return the value of a function and terminate recursion:

int factorial(int n) {
  if (n == 0) {
    return 1; // 基线条件
  }
  else {
    return n * factorial(n - 1);
  }
}

Practical case: Tower of Hanoi problem

The Tower of Hanoi problem is a classic recursive problem that involves moving n disks from one pole to another. Only one disk can be moved at a time, and larger disks cannot be placed on top of smaller disks.

The following is a C function that uses recursion to solve the Tower of Hanoi problem:

void hanoi(int n, int from, int to, int via) {
  if (n == 1) {
    cout << "Move disk 1 from " << from << " to " << to << endl;
    return;
  }
  hanoi(n - 1, from, via, to);
  cout << "Move disk " << n << " from " << from << " to " << to << endl;
  hanoi(n - 1, via, to, from);
}

In this function,

• n is the disk The quantities
• from, to and via are integer values ​​representing the poles

## recursively Application in programming competitions

Recursion is often used in programming competitions because it provides a concise and elegant way to solve complex problems. The following are common applications of recursion in programming competitions:

Solving tree structure problems
• Depth-first search
• Backtracking
• Divide and conquer

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