几种常见的递归算法

阶乘

这个比较简单就不说了。

int factorial(int n) {if (n <= 0){return 0;}else if (n == 1){return 1;}else {return n * factorial(n - 1);}
}

fibonacci
如此简单的算法，复试的时候竟然写错了！😳囧！

int fibonacci(unsigned int n) {if (n == 0){return 0;}else if (n == 1){return 1;}else {return fibonacci(n - 1) + fibonacci(n - 2);}
}

ackerman
这个函数究竟是干嘛的不太清楚。但是感觉跟fabnacci没啥本质区别。

int ackerman(unsigned int m, unsigned int n) {if (m == 0){printf("%d\r\n",n+1);return n + 1;}else if (n == 0){int res = ackerman(m - 1, 1);printf("%d\r\n", res);return res;}else {int res= ackerman(m - 1, ackerman(m, n - 1));printf("%d\r\n", res);return res;}
}

hanoi

提供2个函数，都差不多，当然，其中有一个是我写的。

hannoi的时间复杂度是 $2^n -1$

/*
算法思路：1将 n-1个盘子先放到B座位上
2.将A座上地剩下的一个盘移动到C盘上
3、将n-1个盘从B座移动到C座上
*/
void move(unsigned int x, unsigned int y, unsigned long* count)
{printf("%d--->%d\r\n", x, y);(*count)++;
}void hannuo(int n, char one, char two, char three, unsigned long* count)
{if (n == 1)move(one, three, count); //递归截止条件else{hannuo(n - 1, one, three, two, count);//将 n-1个盘子先放到B座位上move(one, three, count);//将A座上地剩下的一个盘移动到C盘上hannuo(n - 1, two, one, three, count);//将n-1个盘从B座移动到C座上}
}void hanoi(unsigned int a, unsigned int c, unsigned int b, int level, unsigned long* count) {if (level == 1){move(a, c, count);}else {hanoi(a, b, c, level - 1, count);move(a, c, count);hanoi(b, c, a, level - 1, count);}
}