//this code is writen by c++
//this code is in cpp1.cpp
#include <algorithm>
using namespace std;
const int MaxN = 1000;
int N = 0 ;
int Knight_Square[MaxN][MaxN];
//those two arries store the way to get the next step, for example, the next step could be (x+2,y-1)
int step_x[8] = { 2, 1, -1, -2, -2, -1, 1, 2} ;
int step_y[8] = {-1, -2, -2, -1, 1, 2, 2, 1} ;
typedef struct Elem{
int hvl ;
int dir ;
bool operator < (const Elem &a) const {
return hvl < a.hvl ;
}
}Helem ;
//struck of position
typedef struct {
int x, y ;
int dex ;
Helem hd[8];// store the possible next step
}Pos ;
//sort the reachable square according to the number of reachable square of the square
void Bubble_Sort(Helem data[]) {
int i,j;
Helem temp;
for(j=0;j<7;j++) {
for(i=0;i<7-j;i++) {
if(data[i].hvl>=data[i+1].hvl) {
temp = data[i];
data[i] = data[i+1];
data[i+1] = temp;
}
}
}
}
// sample stack of Pos, store the tour
typedef struct STACK{
Pos *p_top;
Pos base[MaxN*MaxN + 1];
STACK() {
p_top = base ;
}
void push(const Pos &a){
(*p_top) = a ;
++p_top ;
}
Pos top() {
return *(p_top – 1) ;
}
void pop() {
–p_top;
}
bool empty(){
return (p_top == base) ;
}
}Stack ;
Stack S ;
//output the result
void output( int G[][MaxN], int N )
{
int i, j;
for (i = 0; i < N; ++i){
for (j = 0; j < N; ++j)
printf(“%5d”, G[i][j]);
puts(“\n”);
}
puts(“\n\n”);
}
//check it if it on the Knight_Square
bool check(int x, int y)
{
if (x < 0 || y < 0 || x >= N || y >= N) return false ;
if (Knight_Square[x][y] != 0) return false ;
return true ;
}
//caluate the number of squares that are reachable
int sum_square(int x, int y)
{
int i;
int tx, ty;
int sum = 0;
for (i = 0; i < 8; ++i){
tx = x + step_x[i];
ty = y + step_y[i];
if (check( tx, ty)) ++sum ;
}
return sum ;
}
//set the heuristic, and sort heuristic through the number of reachable square
void Set_Hval( Pos &k )
{
int i ;
int tx, ty ;
int temp=0;
int j=1;
// printf(“%d,%d\n”,k.x,k.y);
for(i = 0; i < 8; ++i)
{
k.hd[i].hvl =N*N+2;
}
for (i = 0; i < 8; ++i) {
tx = k.x + step_x[i];
ty = k.y + step_y[i];
k.hd[i].dir = i ;
if (check( tx, ty))// check if it on the Knight_Square
{
//caluate the number of squares that are reachable using a single knight’s move, and consider it as a degree
k.hd[i].hvl = sum_square(tx, ty);
temp=k.hd[i].hvl;
}
}
j=1;
//judge if it need to be sorted
for(i = 0; i < 8; ++i)
{
j=j&&((k.hd[i].hvl==temp)||(k.hd[i].hvl==N*N+2));}
if(j==0)
Bubble_Sort(k.hd);//adding the next possible square with lowest degree
}
//judge the tour open or closed
bool open(int x, int y)
{
int i;
int tx, ty;
for (i = 0; i < 8; i++)
{
tx = x + step_x[i];
ty = y + step_y[i];
if(Knight_Square[tx][ty]==1)
{
return false;
}
}
return true;
}
//knight tour
int Knight( Pos &start )
{
int step = 1 ;
bool flag ;
int flag2 = 1;
Pos tmp, top ;
while (!S.empty()) S.pop();
Set_Hval(start);
S.push(start);
Knight_Square[start.x][start.y] = 1 ;
while (!S.empty()) {
top = S.top();
flag = false;//if there is no reachable square, the flag will matain false, and return 3
while (++top.dex < 8){
tmp.x = top.x + step_x[ top.hd[top.dex].dir ];//get the nexy step
tmp.y = top.y + step_y[ top.hd[top.dex].dir ];//get the next step
if (!check(tmp.x, tmp.y)) continue; //if this step is not on the Knight_Square, go to another step.
Knight_Square[tmp.x][tmp.y] = ++step ;
flag = true ;
tmp.dex = -1;
Set_Hval(tmp);
S.push(tmp);
if (step == N*N)// knight tour is finished, then judge it if closed or open, if it is open return 1, else return 2
{
if(open(tmp.x,tmp.y))
flag2=1;
else
{
flag2=2;
}
return flag2;
}
break ;
}
//knight tour is failed, let all unreachable square become -1
if (!flag) {
for(int i=0;i<N;i++)
for(int j=0;j<N;j++)
if(Knight_Square[i][j]==0)
Knight_Square[i][j]= -1 ;
flag2=3;
return flag2;
}
}
return flag2 ;
}
int main()
{
Pos p ;
int judge;//use to judge open or close or no tour
printf(“input boards size 1 ~ %d : “, MaxN – 1);
while (scanf(“%d”, &N) != EOF && N > 0 && N < MaxN)//if input the unlegal number, input again
{
p.dex = -1 ;
memset(Knight_Square, 0, sizeof(Knight_Square));
while (true) {
printf(“input X- intercept of position of start 1 ~ %d : “, N);
scanf(“%d”, &p.x);
p.x–;
printf(“input Y- intercept of position of start 1 ~ %d : “, N);
scanf(“%d”, &p.y);
p.y–;
if (check(p.x, p.y)) break;
puts(“\n please input again “);
}
judge=Knight(p);
if ( judge==1 ) {
puts(” <<open tour>> \n”);
}
else if ( judge==2 ) {
puts(” <<closed tour>> \n”);
}
else if(judge==3 )
{
puts(“\n\ncannot find the tour!!\n”);
}
output( Knight_Square, N );
puts(“—————————-\n—————————-“) ;
printf(“input boards size 1 ~ %d : “, MaxN – 1);
}
return 0;
}
