洛谷P1443 马的遍历

最新推荐文章于 2025-03-10 00:45:59 发布

原创最新推荐文章于 2025-03-10 00:45:59 发布 · 333 阅读

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文章标签：

#Python #输出对齐 #队列 #bfs #全局变量

这篇博客介绍了如何使用C语言和Python实现广度优先搜索（BFS）。C语言版本中，自定义了队列结构，并展示了左对齐、右对齐的输出格式。Python版本则使用了内置的队列模块，同时提供了左对齐、居中、右对齐的字符串格式化输出。两个版本都用于解决最短路径问题，并给出了完整的代码实现。

https://www.luogu.com.cn/problem/P1443

C语言：

队列要自己写：

对齐：

printf("%-5d", -1);//左对齐
printf("%5d", -1);//右对齐

代码：

#include <stdio.h>
#include <stdlib.h>

typedef struct
{
    int x, y;
}Node;

typedef Node Qelemtype;

typedef struct
{
    Qelemtype *base;
    int front;
    int rear;
}squeue;

const int MaxValue = 0x7fffffff, MaxSize = 160005;
int n, m;
int f[405][405], vis[405][405];
int fx[8][2]={{2, 1}, {2, -1}, {1, 2}, {1, -2}, {-1, 2}, {-1, -2}, {-2, 1}, {-2, -1}};
squeue q;

void InitQueue()
{
    q.base = (Qelemtype *)malloc(MaxSize * sizeof(Qelemtype));
    if (!q.base)
        exit(-1);
    q.front = 0;
    q.rear = 0;
}

void PushQueue(Qelemtype x)
{
    if (((q.rear + 1)%MaxSize) == q.front)
    {
        printf("¶ÓÂú\n");
        exit(-1);
    }
    q.base[q.rear] = x;
    q.rear = (q.rear + 1) % MaxSize;
}

Qelemtype PopQueue()
{
    Qelemtype x;

    if (q.front == q.rear)
    {
        printf("¶Ó¿Õ\n");
        exit(-1);
    }
    x = q.base[q.front];
    q.front = (q.front + 1) % MaxSize;
    return x;
}

int EmptyQueue()
{
    if (q.rear == q.front)
        return 1;
    else
        return 0;
}

void bfs(int x, int y)
{
    int i, x1, y1;
    Node n1, n2;

    while(!EmptyQueue())
    {
        n1 = PopQueue();
        vis[n1.x][n1.y] = 0;

        for (i = 0; i<8; i++)
        {
            x1 = n1.x + fx[i][0];
            y1 = n1.y + fx[i][1];
            if (x1 > n || x1 <= 0 || y1 > m || y1 <= 0)
                continue;
            if (f[x1][y1] > f[n1.x][n1.y] + 1 && vis[x1][y1] == 0)
            {
                n2.x = x1;  n2.y = y1;
                f[x1][y1] = f[n1.x][n1.y] + 1;
                PushQueue(n2);
                vis[x1][y1] = 1;
            }
        }
    }

    return ;
}

int main()
{
    int i, x, y, j;
    Node n1;

    scanf("%d%d%d%d", &n, &m, &x, &y);

    for (i = 1; i <= n; i++)
        for (j = 1; j <= m; j++)
            f[i][j] = MaxValue;
    memset(vis, 0, sizeof(vis));
    InitQueue();
    f[x][y] = 0;
    n1.x = x;   n1.y = y;
    PushQueue(n1);
    vis[x][y] = 1;

    bfs(x, y);

    for (i = 1; i <= n; i++)
    {
        for (j = 1; j <= m; j++)
        {
            if (f[i][j] == MaxValue)
                printf("%-5d", -1);
            else
                printf("%-5d", f[i][j]);
        }
        printf("\n");
    }

    return 0;
}

python:

输入对齐：

print("|",format("Ursula","*>20"),"|")    #左对齐
print("|",format("Ursula","*^20"),"|")   #居中对齐
print("|",format("Ursula","*<20"),"|")    #右对齐

全局变量：

只用在函数中加global即可

def f():
    global x, y...

代码：

import queue

class Node(object):
    def __init__(self):
        self.x = None
        self.y = None

def bfs():
    global f, fx, q, vis, n, m
    while not q.empty():
        n1 = q.get()
        vis[n1.x][n1.y] = 0
        for i in range(8):
            x1 = n1.x + fx[i][0]
            y1 = n1.y + fx[i][1]
            if x1 <= 0 or x1 > n or y1 <= 0 or y1 >m:
                continue
            if f[x1][y1] > f[n1.x][n1.y] + 1 and vis[x1][y1]==0:
                f[x1][y1] = f[n1.x][n1.y] + 1
                n2 = Node()
                n2.x = x1
                n2.y = y1
                q.put(n2)
                vis[x1][y1] = 1


s = input()
n0, m0, x0, y0 = s.split(' ')
n = eval(n0)
m = eval(m0)
x = eval(x0)
y = eval(y0)

MaxValue = 0x7fffffff
f = [[MaxValue for i in range(m + 5)] for j in range(n + 5)]
vis = [[0 for i in range(m + 5)] for j in range(n + 5)]
q = queue.Queue(n * m + 5)
fx = [[2, 1], [2, -1], [1, 2], [1, -2], [-1, 2], [-1, -2], [-2, 1], [-2, -1]]

vis[x][y] = 1
f[x][y] = 0
n1 = Node()
n1.x = x
n1.y = y
q.put(n1)
bfs()
for i in range(1, n+1):
    for j in range(1, m+1):
        if f[i][j] == MaxValue:
            print(format(-1, " <5"), end='')
        else:
            print(format(f[i][j], " <5"), end='')
    print(end='\n')