1003 Emergency (25) python

题目大意:

输入了医疗队的编号和他们之间相连接需要的条数

输出指定的两个医疗队的最短路径的条数,并且在最短路径中能聚集的医疗队的数量

例子:0到2的最短路径可以是0-2.0-1-2.他们都是2的距离,但是0-1-2能聚集1+2+1的医疗队,输出4

 

用到深度优先算法:尽可能深的搜索,当节点所在的边被探寻过或者不满足条件时,回朔到上一步,反复进行该过程直到所有的点遍历

普适模板:

void dfs(int step):
{
    if 判断边界条件
    {
        
    }
    for 尝试每一种可能
    {
         if判断满足条件
         标记
         继续下一步的dfs
         恢复初始状态
    }
}
inf = float('inf')
cities_num, roads_num, city_start, city_end = map(int,input().split())
rescue_teams = list(map(int,input().split()))
roads = [[inf for i in range(cities_num)] for i in range(cities_num)] #横纵座标为两个点,数值为距离
visit = [0 for i in range(cities_num)] #访问节点列表
min_roads = inf #最短路径
min_roads_count = 0 #最短路径条数
max_resue_sum =0 #最大救援队个数

for i in range(roads_num):
    city1, city2, road = map(int,input().split())
    roads[city1][city2] = road
    roads[city2][city1] = road

def dfs(start, end, road, resue):
    global min_roads, min_roads_count, max_resue_sum,roads_num,rescue_teams,visit
    if(start == end):
        if(road < min_roads): #如果小于当前的road数则更新
            min_roads_count = 1
            min_roads = road
            max_resue_sum = resue
        elif(road == min_roads):#如果等於则更新营救队的最大个数
            min_roads_count += 1
            if(max_resue_sum < resue):
                max_resue_sum = resue
        return 0
    if(road > min_roads):
        return 1
    for i in range(cities_num):
        if(visit[i] == 0 and roads[start][i] != inf):
            visit[i] = 1
            dfs(i, end, road+roads[start][i], resue+rescue_teams[i])
            visit[i] = 0

visit[city_start] = 1
dfs(city_start,city_end,0,rescue_teams[city_start])
print(min_roads_count,max_resue_sum)

 

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