70 lines
1.6 KiB
JavaScript
70 lines
1.6 KiB
JavaScript
/**
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* File: recursion.js
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* Created Time: 2023-08-28
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* Author: Gaofer Chou (gaofer-chou@qq.com)
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*/
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/* Recursion */
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function recur(n) {
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// Termination condition
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if (n === 1) return 1;
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// Recursive: recursive call
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const res = recur(n - 1);
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// Return: return result
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return n + res;
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}
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/* Simulate recursion with iteration */
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function forLoopRecur(n) {
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// Use an explicit stack to simulate the system call stack
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const stack = [];
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let res = 0;
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// Recursive: recursive call
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for (let i = n; i > 0; i--) {
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// Simulate "recursive" by "pushing onto the stack"
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stack.push(i);
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}
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// Return: return result
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while (stack.length) {
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// Simulate "return" by "popping from the stack"
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res += stack.pop();
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}
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// res = 1+2+3+...+n
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return res;
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}
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/* Tail recursion */
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function tailRecur(n, res) {
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// Termination condition
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if (n === 0) return res;
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// Tail recursive call
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return tailRecur(n - 1, res + n);
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}
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/* Fibonacci sequence: Recursion */
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function fib(n) {
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// Termination condition f(1) = 0, f(2) = 1
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if (n === 1 || n === 2) return n - 1;
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// Recursive call f(n) = f(n-1) + f(n-2)
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const res = fib(n - 1) + fib(n - 2);
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// Return result f(n)
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return res;
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}
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/* Driver Code */
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const n = 5;
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let res;
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res = recur(n);
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console.log(`递归函数的求和结果 res = ${res}`);
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res = forLoopRecur(n);
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console.log(`使用迭代模拟递归的求和结果 res = ${res}`);
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res = tailRecur(n, 0);
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console.log(`尾递归函数的求和结果 res = ${res}`);
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res = fib(n);
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console.log(`斐波那契数列的第 ${n} 项为 ${res}`);
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