alogorithm: random walk and a knight's tour

数据结构第2章花了2个礼拜才搞定，工作忙，业余时间少了。

总结2个算法:随机漫步和骑士旅行（题目参见p62）

随机漫步：一只大蟑螂在m*n的格子上随机行走，经过多少次可以走遍整个格子

 

// algorithm random walk.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include <iostream>#include <time.h>using namespace std;//Current status of bugstruct status{int x, y;int passed;int iterated;};//Map informationstruct maps{int iLength, iWideth;int **p;};class randomwalk{public:randomwalk(int iLen, int iWide, int max_iter);~randomwalk();int walk(int i);void algorithm();void printWalk();private:struct status m_stStatus;struct maps m_stMap;int m_iMaxIter;};//Init map and statusrandomwalk::randomwalk(int iLen, int iWide, int max_iter){m_stMap.iLength = iLen;m_stMap.iWideth = iWide;m_stMap.p = new int *[iLen];int i, j;for(i = 0; i < iLen; ++i){m_stMap.p[i] = new int[iWide];}for(i = 0 ; i < iLen; ++i)for(j = 0; j < iWide; ++j)m_stMap.p[i][j] = 0;//random the position of bug, passed grid is 0m_stStatus.passed = 0;m_stStatus.iterated = 0;m_stStatus.x = rand()%(iLen - 1);m_stStatus.y = rand()%(iWide - 1);m_iMaxIter = max_iter;}randomwalk::~randomwalk(){for(int i = 0; i < m_stMap.iLength; ++i)delete []m_stMap.p[i];delete []m_stMap.p;}//judge if walk is legal , if walk return 1, else return 0int randomwalk::walk(int i){switch(i){case 0:if(m_stStatus.x > 0 && m_stStatus.y < (m_stMap.iWideth - 1)){m_stStatus.x--;m_stStatus.y++;return 1;}return 0;case 1:if(m_stStatus.y < (m_stMap.iWideth - 1)){m_stStatus.y++;return 1;}return 0;case 2:if(m_stStatus.x < (m_stMap.iLength - 1) && m_stStatus.y < (m_stMap.iWideth -1) ){m_stStatus.x++;m_stStatus.y++;return 1;}return 0;case 3:if(m_stStatus.x <(m_stMap.iLength - 1)){m_stStatus.x++;return 1;}return 0;case 4:if(m_stStatus.x < (m_stMap.iLength - 1) && m_stStatus.y > 0){m_stStatus.x++;m_stStatus.y--;return 1;}return 0;case 5:if(m_stStatus.y >0){m_stStatus.y--;return 1;}return 0;case 6:if(m_stStatus.x >0 && m_stStatus.y > 0){m_stStatus.x--;m_stStatus.y--;return 1;}return 0;case 7:if(m_stStatus.x > 0){m_stStatus.x--;return 1;}return 0;default:printf("Error walk");return 0;}}//walk all gridsvoid randomwalk::algorithm(){while(m_stStatus.passed < (m_stMap.iLength*m_stMap.iWideth) && m_stStatus.iterated < m_iMaxIter){int rnd = rand()%8;if(walk(rnd)){int i = m_stStatus.x, j = m_stStatus.y;if(m_stMap.p[i][j] == 0){m_stStatus.passed++;}m_stMap.p[i][j]++;m_stStatus.iterated++;}}}void randomwalk::printWalk(){printf("Walk times is %d.\n", m_stStatus.iterated);for(int i = 0; i < m_stMap.iLength; ++i){for(int j = 0; j< m_stMap.iWideth; ++j){printf("%3d ", m_stMap.p[i][j]);}printf("\n");}}int _tmain(int argc, _TCHAR* argv[]){srand((int)time(0));class randomwalk *pcRandWalk;pcRandWalk = new randomwalk(15, 15, 50000);pcRandWalk->algorithm();pcRandWalk->printWalk();delete pcRandWalk;return 0;}

骑士旅行：一个国际象棋棋盘，随机一个位置（i，j），在不重复的情况下走L步，走遍整个棋盘。

算法：board[8][8] = {0};当位于(i,j)时，下一步pos = movpos(i,j)，if(pos = 0 ) 退出，打印；else 存储下一步的可能的坐标；

            对可能的坐标 posnext = movpos(nextx,nexty); 找到最小的posnext，并把该坐标 = 当前坐标，mboard[i][j] = count++；

 代码如下：也可以采用递归，我这个方法比较2，各位看官谅解。

// knight's tour.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include <iostream>int ktmove1[8] = {-2,-1,1,2,2,1,-1,-2};int ktmove2[8] = {1,2,2,1,-1,-2,-2,-1};struct coordinate{int x, y;};struct nextpos{int nextx[8], nexty[8];int pos;};class lshaped{public:lshaped(int x, int y);int movepos(int x, int y, struct nextpos *pnext);int move();void print();private:int m_board[8][8];int m_count;struct coordinate m_stCondition;struct nextpos m_stNextPos;bool m_flag;};//init boardlshaped::lshaped(int x, int y){for(int i = 0; i < 8; ++i)for(int j = 0; j < 8; ++j)m_board[i][j] = 0;m_stCondition.x = x;m_stCondition.y = y;m_count = 0;m_flag = 1;memset(&m_stNextPos, 0, sizeof(m_stNextPos));}//possible move position and return numint lshaped::movepos(int x, int y, struct nextpos *pnext){pnext->pos = 0;for(int i = 0; i < 8; ++i){if( (x + ktmove1[i]) < 8 && (x + ktmove1[i]) >= 0 &&(y + ktmove2[i]) < 8 && (y + ktmove2[i]) >= 0 &&((x + ktmove1[i])!= 3 || (y + ktmove2[i])!=3) &&m_board[x + ktmove1[i]][y + ktmove2[i]] == 0){pnext->nextx[pnext->pos] = x + ktmove1[i];pnext->nexty[pnext->pos] = y + ktmove2[i];pnext->pos++;}}return pnext->pos;}//begin to move, loop movepos, if pos = 0;printf else min = movepos(x[i],y[i]), postion + [min];int lshaped::move(){int i;int num, min = 8;int index;struct nextpos *ptemp = NULL;i = movepos(m_stCondition.x, m_stCondition.y, &m_stNextPos);if(i == 0){return 1;}ptemp = (struct nextpos *)malloc(sizeof(struct nextpos));memcpy(ptemp, &m_stNextPos, sizeof(struct nextpos));for(int j = 0 ; j < i; ++j){num = movepos( m_stNextPos.nextx[j],m_stNextPos.nexty[j], ptemp );if(num < min){min = num;index = j;}}free(ptemp);m_stCondition.x = m_stNextPos.nextx[index];m_stCondition.y = m_stNextPos.nexty[index];m_board[m_stCondition.x][m_stCondition.y] = ++m_count;return 0;}void lshaped::print(){for(int i = 0; i < 8; ++i){for(int j = 0; j < 8; ++j){printf("%2d ", m_board[i][j]);}printf("\n");}}int _tmain(int argc, _TCHAR* argv[]){class lshaped example(3, 3);int flag = 1;while(flag){if(example.move())flag = 0;}example.print();return 0;}