迭代算法

fib-arr1.js

//

start = new Date();

function fib(n) {

var x = 0;

var y = 1;

var z = 0;

if(n == 0){

return x;

} else if (n == 1) {

return y;

}

else{

for (let i = 0; i <= n-2; i++) {

z = x + y;

x = y;

y = z;

}

return z;

}

}

//

p = 40;

var arrf = [];

for (let i = 0; i < p; i++) {

m = fib(i);

arrf.push(m);

};

console.log(arrf);

//

end = new Date();

time = end.getTime() - start.getTime();

console.log("The cost time is :" + time + "ms");

运行结果：

[ 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, ... 39088169, 63245986 ]

The cost time is :65ms

迭代算法会重复的循环运算，并将运算结果通过赋值的形式，追加到新的运算中来求出新的结果。

递归算法

fib-arr2.js

//

start = new Date();

function fib(n){

if(n == 0) {

return 0;

} else if (n == 1) {

return 1;

} else {

return fib(n - 1) + fib(n - 2);

}

}

//

p = 40;

var arrf = [];

for (let i = 0; i < p; i++) {

m = fib(i);

arrf.push(m);

};

console.log(arrf);

//

end = new Date();

time = end.getTime() - start.getTime();

console.log("The cost time is :" + time + "ms");

运行结果：

[ 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 87, 1597, ... 39088169,

63245986 ]

The cost time is :7368ms

递归算法会循环的引用，将每次计算的过程引入下一次计算中，最后一次运算出结果。

运行环境是Windows上的node.js，Linux上会更快些。