POJ-2243

#include <stdio.h>#include <string.h>int chessboard[8][8];char s1[2], s2[2];int queue[100], top, rear;int position[8][2] = {{-2, 1}, {-1, 2}, {1, 2}, {2, 1}, {2, -1}, {1, -2}, {-1, -2}, {-2, -1}};void bfs(void){     int i, x, y, temp1, temp2;     do {        x = queue[top]/10;        y = queue[top]%10;        top++;        top %= 100;        for (i = 0; i < 8; i++) {            temp1 = x+position[i][0];            temp2 = y+position[i][1];            if (temp1 >=0 && temp1 < 8 && temp2 >= 0 && temp2 < 8 && chessboard[temp1][temp2] == -1) {               ++rear;               rear %= 100;               queue[rear] = temp1*10 + temp2;   chessboard[temp1][temp2] = x*10+y;               if (temp1 == s2[0]-'a' && temp2 == s2[1]-'1')                  return;            }        }     }while (top != rear);}int main(){    int num, n, i, j;    while (scanf("%s%s", s1, s2) == 2) {          top =rear = 0;          for (i = 0; i < 8; i++)              for (j = 0; j < 8; j++)                  chessboard[i][j] = -1;          chessboard[s1[0]-'a'][s1[1]-'1'] = queue[rear] = (s1[0]-'a')*10 + s1[1]-'1';          num = 0;          if (s1[0] != s2[0] || s1[1] != s2[1]) {             bfs();             num = 1;          }          i = s2[0]-'a';          j = s2[1]-'1';          for (; chessboard[i][j] != (s1[0]-'a')*10 + s1[1]-'1'; num++) {  n = chessboard[i][j];              i = n/10;              j = n%10;          }          printf("To get from %s to %s takes %d knight moves.\n", s1, s2, num);            }    return 0;}