UVa 439 - Knight Moves (BFS)

题意

思路

AC代码

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

int k[10][10], vis[10][10], pre[300];
int turn[8][2] = {{-2,1},{-1,2},{1,2},{2,1},{2,-1},{1,-2},{-1,-2},{-2,-1}};
int x1, y1, x2, y2;

struct POINT
{
int x, y;
}que[300];

int cnt;

void cntpls( int a ){
int t = pre[a];
if( t != 0 )
cntpls(t);
cnt++;
}

void Print( int n )
{
cntpls(n);
printf("To get from %c%d to %c%d takes %d knight moves.\n",y1+'a',8-x1,y2+'a',8-x2,cnt);
}

bool go( int x, int y )
{
if( x >= 0 && x < 8 && y >= 0 && y < 8 )
return true;
return false;
}

void BFS()
{
cnt = 0;
memset(vis, 0, sizeof(vis));
int head = 0, tile = 1, a, b, xx, yy;
que[0].x = x1;
que[0].y = y1;
pre[0] = -1;
while( head < tile ){
a = que[head].x;
b = que[head].y;
if( a == x2 && b == y2 ){
Print(head);
return;
}
for( int i = 0; i < 8; i++ ){
xx = a + turn[i][0];
yy = b + turn[i][1];
if( !vis[xx][yy] && go(xx, yy) ){
//cout << xx << " " << yy << endl;
vis[xx][yy] = 1;
que[tile].x = xx;
que[tile].y = yy;
pre[tile] = head;
tile++;
}
}
head++;
}
return;
}

int main()
{
char s[5];
while( gets(s) != NULL )
{
x1 = 8 - ( s[1] - '0' );
y1 = s[0] - 'a';
x2 = 8 - ( s[4] - '0' );
y2 = s[3] - 'a';
if( x1 == x2 && y1 == y2 )
printf("To get from %c%d to %c%d takes 0 knight moves.\n",y1+'a',8-x1,y2+'a',8-x2);
else
BFS();
}
return 0;
}