【HDOJ】2645 find the nearest station

裸BFS。

/* 2645 */
#include <iostream>
#include <queue>
#include <cstdio>
#include <cstring>
#include <cstdlib>
using namespace std;

#define MAXN 200

typedef struct node_t {
    int x, y;
    node_t() {}
    node_t(int xx, int yy) {
        x = xx; y = yy;
    }
} node_t;

int n, m;
queue<node_t> Q;
char map[MAXN][MAXN];
int dist[MAXN][MAXN];
int dir[4][2] = {
    -1,0,1,0,0,-1,0,1
};

void bfs() {
    int i, j, k;
    int x, y;
    node_t nd;
    
    while (!Q.empty()) {
        nd = Q.front();
        Q.pop();
        for (i=0; i<4; ++i) {
            x = nd.x + dir[i][0];
            y = nd.y + dir[i][1];
            if (x<0 || x>=n || y<0 || y>=m || map[x][y]=='1')
                continue;
            map[x][y] = '1';
            dist[x][y] = dist[nd.x][nd.y] + 1;
            Q.push(node_t(x, y));
        }
    }
}

int main() {
    int i, j, k;
    
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
    #endif
    
    while (scanf("%d %d", &n, &m) != EOF) {
        for (i=0; i<n; ++i) {
            scanf("%s", map[i]);
            for (j=0; j<m; ++j) {
                if (map[i][j] == '1') {
                    Q.push(node_t(i, j));
                    dist[i][j] = 0;
                }
            }
        }
        bfs();
        for (i=0; i<n; ++i) {
            printf("%d", dist[i][0]);
            for (j=1; j<m; ++j)
                printf(" %d", dist[i][j]);
            printf("
");
        }
    }
    
    return 0;
}