pku 1915 Knight Moves 双向BFS

最简单的双向BFS, 就不做注释和说明了-_-

 

 

#include <stdio.h> #include <iostream> #include <string.h> #include <queue> using namespace std; struct Point{ int x, y; Point(int _x, int _y){x = _x; y = _y;} }; int startx, starty, endx, endy; int n; int visit[2][300][300]; int dx[] = {-2, -1, 1, 2, 2, 1, -1, -2}; int dy[] = {-1, -2, -2, -1, 1, 2, 2, 1}; inline bool ok(int x, int y) { if(x < 0 || x >= n || y < 0 || y >= n) return false; return true; } int bfs() { queue<Point> q[2]; q[0].push(Point(startx, starty)); q[1].push(Point(endx, endy)); visit[0][starty][startx] = visit[1][endy][endx] = 0; while(!q[0].empty() && !q[1].empty()) { if(!q[0].empty()) { Point p = q[0].front(); q[0].pop(); for(int i = 0; i < 8; ++i) { int tempx = p.x + dx[i], tempy = p.y + dy[i]; if(ok(tempx, tempy) && visit[0][tempy][tempx] == -1) { if(visit[1][tempy][tempx] >= 0) return visit[0][p.y][p.x]+visit[1][tempy][tempx]+1; q[0].push(Point(tempx, tempy)); visit[0][tempy][tempx] = visit[0][p.y][p.x]+1; } } } if(!q[1].empty()) { Point p = q[1].front(); q[1].pop(); for(int i = 0; i < 8; ++i) { int tempx = p.x + dx[i], tempy = p.y + dy[i]; if(ok(tempx, tempy)&& visit[1][tempy][tempx] == -1) { if(visit[0][tempy][tempx] >= 0) return visit[1][p.y][p.x]+visit[0][tempy][tempx]+1; q[1].push(Point(tempx, tempy)); visit[1][tempy][tempx] = visit[1][p.y][p.x]+1; } } } } return -1; } int main() { int N; scanf("%d", &N); while (N--) { scanf("%d", &n); scanf("%d%d", &starty, &startx); scanf("%d%d", &endy, &endx); if(startx == endx && starty == endy) { printf("0/n"); continue; } memset(visit, -1, sizeof(visit)); printf("%d/n", bfs()); } return 0; }