16叉树

#include <iostream>
#include <cstdio>
using namespace std;

const int M = 16;
struct node{
	node(int _v = 0, int _n = 0): value(_v), num(_n){
		for(int i = 0; i < M; i++) next[i] = NULL;
	}
	int value, num;
	node* next[M];
};

const int N = 290;
int a[N];
int *p;
int tree[9] = {0,1,17,273,4369,69905,1118481,17895697,286331153};

int calChildNum(int total, int remain, int index){
	if(total - tree[index+1] >= (remain - 1) * tree[index]) return tree[index+1];
	else return total - (remain - 1) * tree[index];
}

node* creat(int num){
	node* buf = new node(*p++, num);
	int index = 0;
	for(int i = 8; i >= 0; i--) {
		if(num > tree[i]) {
			index = i - 1;
			break;
		}
	}
	num--;
	for(int i = M; i > 0; i--){
		if(num <= 0) break;
		int k = calChildNum(num, i, index);
		num -= k;
		if(k > 0) buf->next[M-i] = creat(k);
	}
	return buf;
}

void print(node* root){
	cout << root->value << endl;
	for(int i = 0; i < M; i++)if(root->next[i]) print(root->next[i]);
}
int get(node* root, int index){
	if(index == 1) return root->value;
	else{
		index--;
		for(int i = 0; i < M; i++){
			if(index <= root->next[i]->num) return get(root->next[i], index);
			index -= root->next[i]->num;
		}
	}
}

int main(){
	for(int i = 0; i < N-1; i++) a[i] = i + 1;
	p = a;
	node* root = creat(N-1);
	for(int i = 0; i < N-1; i++) cout << get(root, i + 1) << endl;
	return 0;
}

不可变数据结构中的数组是用16叉树或者32叉树实现的，自己用c++写了写，发现不适合用命令式语言搞这些东西，而且我的效率很差

真不知道函数式语言是如何实现的