利用本章末尾描述的算法（散列表加速）实现字谜程序

数据结构与算法分析——c语言描述 练习5.13 a 答案

hashQuad.h

typedef char* ElementType;

#ifndef _HashQuad_H
#define _HashQuad_H

typedef unsigned int Index;
typedef Index Position;

struct HashTbl;
typedef struct HashTbl* HashTable;

HashTable initializeTable(int tableSize);
void destroyTable(HashTable h);
Position find( const char * key, HashTable h);
HashTable insert(ElementType key, HashTable h);
HashTable rehash(HashTable h);
ElementType retrive(Position p, HashTable h);
int isLegitimate(Position pos, HashTable h);
#endif

hashQuad.cpp

#include"hashQuad.h"
#include"fatal.h"
#include<math.h>
#include<string.h>
#define MinTableSize 10

enum KindOfEntry { Legitimate, Empty, Deleted };

struct HashEntry {
	ElementType element;
	enum KindOfEntry info;
};

typedef struct HashEntry Cell;

struct HashTbl {
	int tableSize;
	int hasInsertedNum;
	Cell *theCells;//数组
};

static int hash(const char * key, int tableSize) {
	unsigned int hashVal = 0;
	while (*key != '\0')
		hashVal = (hashVal << 5) + *key++;
	return hashVal % (tableSize);
}
static int isPrime(int num) {
	for (int i = 2; i <= sqrt(num); i++)
		if (num%i == 0)
			return 0;
	return 1;
}
static int nextPrime(int num) {
	int i = num;
	while (!isPrime(i))
		i++;
	return i;
}

int isLegitimate(Position pos, HashTable h) {
	return h->theCells[pos].info == Legitimate;
}


HashTable initializeTable(int tableSize) {
	HashTable h;
	int i;
	if (tableSize < MinTableSize) {
		Error("Table size too small");
		return NULL;
	}
	h = (HashTable)malloc(sizeof(struct HashTbl));
	if (h == NULL)
		FatalError("Out of space!!!");
	h->tableSize = nextPrime(tableSize);
	h->theCells = (Cell*)malloc(sizeof(Cell)*h->tableSize);
	h->hasInsertedNum = 0;
	if (h->theCells == NULL)
		FatalError("Out of space!!!");
	for (i = 0; i < h->tableSize; i++) {
		h->theCells[i].info = Empty;
	}
	return h;
}

void destroyTable(HashTable h) {
	for (int i = 0; i < h->tableSize; i++)
		if (h->theCells[i].info == Legitimate)
			free(h->theCells[i].element);
	free(h->theCells);
	free(h);
}

Position find(const char *key , HashTable h) {
	Position currentPos = hash(key, h->tableSize);
	while (h->theCells[currentPos].info != Empty && strcmp(h->theCells[currentPos].element, key) != 0) {
		currentPos = (currentPos + 1) % h->tableSize;
	}
	return currentPos;
}

HashTable insert(ElementType key, HashTable h) {
	if ((double)h->hasInsertedNum / h->tableSize > 0.5)
		h = rehash(h);
	Position pos = find(key, h);
	if (h->theCells[pos].info != Legitimate) {
		h->theCells[pos].element =(char *) malloc(sizeof(char)*strlen(key) + 1);
		strcpy(h->theCells[pos].element, key);
		h->theCells[pos].info = Legitimate;
		h->hasInsertedNum++;
	}
	return h;
}

HashTable rehash(HashTable h) {
	HashTable newH = initializeTable(h->tableSize * 2);
	for (int i = 0; i < h->tableSize; i++)
		if (h->theCells[i].info == Legitimate)
			insert(h->theCells[i].element, newH);
	destroyTable(h);
	return newH;
}



ElementType retrive(Position p, HashTable h) {
	return h->theCells[p].element;
}

main.cpp

#include<stdio.h>
#include<string>
#include<algorithm>
#include"hashQuad.h"

#define MAXN 100

char dictionary[MAXN][MAXN];
char table[MAXN][MAXN];//字谜

					   //由上顺时针旋转一圈
int dx[8] = { 0,1,1,1,0,-1,-1,-1 };
int dy[8] = { 1,1,0,-1,-1,-1,0,1 };

int dic_num, n;

int main() {
	int i;
	HashTable h = initializeTable(100);
	scanf("%d%d", &dic_num, &n);

	for (i = 0; i < dic_num; i++) {
		scanf("%s", dictionary[i]);
		h = insert(dictionary[i], h);
	}

	for (i = 0; i < n; i++) {
		scanf("%s", table[i]);
	}

	for (int r = 0; r < n; r++) {
		for (int c = 0; c < n; c++) {
			for (int d = 0; d < 8; d++) {
				std::string s;
				int rr = r;
				int cc = c;
				for (int l = 1; l <= n; l++) {
					s += table[rr][cc];
					rr += dx[d];
					cc += dy[d];
					/*
					for (int i = 0; i < dic_num; i++) {
						if (strcmp(s.c_str(), dictionary[i]) == 0) {
							printf("%s\n", s.c_str());
							break;
						}
					}
					*/
					Position pos = find(s.c_str(), h);
					if(isLegitimate(pos,h))
						printf("%s\n", s.c_str());
				}
			}
		}
	}
}