裸干usaco prime3

最新推荐文章于 2021-11-17 14:03:56 发布

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最新推荐文章于 2021-11-17 14:03:56 发布

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分类专栏：信息学文章标签： tree null insert rest delete file

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本文深入探讨了USACO Prime3比赛中的数据结构和算法应用，包括树的操作、空节点处理、元素插入、休息策略及文件处理等关键点，旨在帮助参赛者提升竞赛水平。

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[手动搬家自网易博客原发表日期：2009-07-24 15:13 ]

刚在网上查了一下usaco prime3，发现还是有不少优化，可惜我都没用，只是写了一个比较暴力的数据结构（好像叫字典树？）+明显的剪枝。程序写了320行（包括一些debug用的东西），汗……

无辜的代码飘过：

/*
 * $File: prime3.cpp
 * $Date: Fri Jul 24 14:58:57 2009
ID: gy_jk2
LANG: C++
TASK: prime3
 */
#define INPUT	"prime3.in"
#define OUTPUT	"prime3.out"
//#define DEBUG 1
#ifdef DEBUG
#include <iostream>
using namespace std;
#endif
#include <cstdio>
#include <cassert>
#include <cstring>
namespace Solve
{
	struct Tree_node
	{
		int val;
		Tree_node *child, *brother, *parent;
		Tree_node(int v, Tree_node *b = NULL, Tree_node *p = NULL) : val(v), child(NULL), brother(b), parent(p) {}
		~Tree_node() {if (child != NULL) delete child; if (brother != NULL) delete brother;}
	};
	Tree_node *prime_tree;
	void insert_into_tree(int num, int rest_depth, Tree_node *root);
	// insert @num into @root in !reverse! order (e.g, 123 -> 321)
	Tree_node* find_in_cur_level(int num, Tree_node *root);
	// return NULL if nothing found.
	
#ifdef DEBUG
	void print_tree(Tree_node *root, int n)
	{
		if (root->child == NULL)
			cout << n << endl;
		for (Tree_node *ptr = root->child; ptr != NULL; ptr = ptr->brother)
			print_tree(ptr, n * 10 + ptr->val);
	}
#endif
	const int PRIME_RANGE_BEGIN = 10000, PRIME_RANGE_END = PRIME_RANGE_BEGIN * 10;
	void init_prime(int sum);
	int square[5][5];
	Tree_node *root_row[5], *root_diagonal[2];
	int digit_usable[5][5];
	void dfs(int row, int col, Tree_node *root);
	const char *NO_ANSWER = "NONE/n";
	struct Answer
	{
		int square[5][5];
		Answer *next;
		Answer(Answer *n) : next(n) {memcpy(this->square, Solve::square, sizeof(Solve::square));}
		bool operator < (const Answer &n);
	};
	Answer *answer, **answer_array;
	int nanswer;
	void solve(FILE *fin, FILE *fout);
}
void Solve::solve(FILE *fin, FILE *fout)
{
	int n0, sum;
	assert(fscanf(fin, "%d %d", ∑, &n0) == 2);
	init_prime(sum);
#ifdef DEBUG
	print_tree(prime_tree, 0);
#endif
	for (int i = 0; i < 5; i ++)
	{
		for (int j = 0; j < 5; j ++)
			if (i == 0 && j == 0)
				digit_usable[i][j] = 1 << n0;
			else digit_usable[i][j] = 0xFFF;
		root_row[i] = prime_tree;
	}
	root_diagonal[0] = root_diagonal[1] = prime_tree;
	dfs(0, 0, prime_tree);
	if (answer != NULL)
	{
		answer_array = new Answer*[nanswer];
		int pos = 0;
		for (Answer *ptr = answer; ptr != NULL; ptr = ptr->next)
			answer_array[pos ++] = ptr;
		for (int i = 1; i < nanswer; i ++)
		{
			Answer *key = answer_array[i];
			pos = i - 1;
			while (pos >= 0 && (*key) < (*answer_array[pos]))
			{
				answer_array[pos + 1] = answer_array[pos];
				pos --;
			}
			answer_array[pos + 1] = key;
		}
		for (int i = 0; i < nanswer; i ++)
		{
			if (i)
				fprintf(fout, "/n");
			for (int x = 0; x < 5; x ++)
			{
				for (int y = 0; y < 5; y ++)
					fprintf(fout, "%d", answer_array[i]->square[x][y]);
				fprintf(fout, "/n");
			}
			delete answer_array[i];
		}
		delete []answer_array;
	} else fprintf(fout, "%s", NO_ANSWER);
	delete prime_tree;
}
bool Solve::Answer::operator < (const Answer &n)
{
	for (int i = 0; i < 5; i ++)
		for (int j = 0; j < 5; j ++)
			if (square[i][j] < n.square[i][j])
				return true;
			else if (square[i][j] > n.square[i][j])
				return false;
	return false;
}
Solve::Tree_node* Solve::find_in_cur_level(int num, Tree_node *root)
{
	if (root == NULL)
		return NULL;
	Tree_node *pos = root->child;
	while (pos != NULL && pos->val < num)
		pos = pos->brother;
	if (pos == NULL || pos->val > num)
		return NULL;
	return pos;
}
void Solve::dfs(int row, int col, Tree_node *root)
{
	if (row == 5)
	{
		row = 0;
		col ++;
		if (col == 5)
		{
			answer = new Answer(answer);
			nanswer ++;
			return;
		}
		root = prime_tree;
	}
	if (col == 4)
	{
		int du = digit_usable[row][col];
		int &sq = square[row][col];
		for (Tree_node *ptr = root->child; ptr != NULL; ptr = ptr->brother)
			if (du & (1 << ptr->val))
			{
				sq = ptr->val;
				dfs(row + 1, col, ptr);
			}
		return;
	}
	int du = digit_usable[row][col];
	int &sq = square[row][col];
	bool d0 = (row == col), d1 = (row + col == 4);
	int u0 = digit_usable[row][col + 1], u1 = 0, u2 = 0;
	if (d0)
		u1 = digit_usable[row + 1][col + 1];
	if (d1)
		u2 =  digit_usable[row - 1][col + 1];
	for (Tree_node *ptr = root->child; ptr != NULL; ptr = ptr->brother)
		if (du & (1 << ptr->val))
		{
			Tree_node *r0 = find_in_cur_level(sq = ptr->val, root_row[row]), *r1 = NULL, *r2 = NULL;
			if (r0 == NULL)
				continue;
			if (d0)
			{
				if ((r1 = find_in_cur_level(ptr->val, root_diagonal[0])) == NULL)
					continue;
			}
			if (d1)
			{
				if ((r2 = find_in_cur_level(ptr->val, root_diagonal[1])) == NULL)
					continue;
			}
			root_row[row] = r0;
			int mask = 0;
			for (Tree_node *p = r0->child; p != NULL; p = p->brother)
				mask |= 1 << p->val;
			if ((digit_usable[row][col + 1] = u0 & mask) == 0)
			{
				root_row[row] = r0->parent;
				continue;
			}
			if (d0)
			{
				root_diagonal[0] = r1;
				mask = 0;
				for (Tree_node *p = r1->child; p != NULL; p = p->brother)
					mask |= 1 << p->val;
				if ((digit_usable[row + 1][col + 1] = u1 & mask) == 0)
				{
					root_row[row] = r0->parent;
					root_diagonal[0] = r1->parent;
					continue;
				}
			}
			if (d1)
			{
				root_diagonal[1] = r2;
				mask = 0;
				for (Tree_node *p = r2->child; p != NULL; p = p->brother)
					mask |= 1 << p->val;
				if ((digit_usable[row - 1][col + 1] = u2 & mask) == 0)
				{
					root_row[row] = r0->parent;
					if (d0)
						root_diagonal[0] = r1->parent;
					root_diagonal[1] = r2->parent;
					continue;
				}
			}
			dfs(row + 1, col, ptr);
			root_row[row] = r0->parent;
			if (d0)
				root_diagonal[0] = r1->parent;
			if (d1)
				root_diagonal[1] = r2->parent;
		}
	digit_usable[row][col + 1] = u0;
	if (d0)
		digit_usable[row + 1][col + 1] = u1;
	if (d1)
		digit_usable[row - 1][col + 1] = u2;
}
void Solve::insert_into_tree(int num, int rest_depth, Tree_node *root)
{
	if (rest_depth == 0)
		return;
	Tree_node *pos = root->child, *last = NULL;
	int digit = num % 10;
	while (pos != NULL && pos->val < digit)
	{
		last = pos;
		pos = pos->brother;
	}
	if (pos != NULL && pos->val == digit)
		insert_into_tree(num / 10, rest_depth - 1, pos);
	else if (last == NULL)
		insert_into_tree(num / 10, rest_depth - 1, root->child = new Tree_node(digit, root->child, root));
	else insert_into_tree(num / 10, rest_depth - 1, last->brother = new Tree_node(digit, pos, root));
}
void Solve::init_prime(int sum)
{
	unsigned int tmp[PRIME_RANGE_END / 32 + 1] = {0};
	prime_tree = new Tree_node(-1);
#ifdef DEBUG
	const int P[] = {11351, 14033, 30323, 53201, 13313, 14303, 13331};
	for (int i = 0; i < 7; i ++)
	{
		int n1 = 0;
		for (int j = P[i]; j; j /= 10)
			n1 = n1 * 10 + (j % 10);
		insert_into_tree(n1, 5, prime_tree);
	}
	return;
#endif
#define VISIT(_p_) (tmp[(_p_) >> 5] & (1 << ((_p_) & 31)))
#define SET(_p_) tmp[(_p_) >> 5] |= (1 << ((_p_) & 31))
	for (int i = 2; i < PRIME_RANGE_END; i ++)
		if (VISIT(i) == 0)
		{
			if (i >= PRIME_RANGE_BEGIN)
			{
				int s = 0, n1 = 0;
				for (int j = i; j; j /= 10)
				{
					s += j % 10;
					n1 = n1 * 10 + (j % 10);
				}
				if (s == sum)
					insert_into_tree(n1, 5, prime_tree);
			}
			for (int j = i * 2; j < PRIME_RANGE_END; j += i)
				SET(j);
		}
#undef VISIT
#undef SET
}
int main()
{
	FILE *fin = fopen(INPUT, "r"), *fout = fopen(OUTPUT, "w");
	Solve::solve(fin, fout);
	fclose(fin);
	fclose(fout);
}