1003 Emergency (25) python

題目大意:

輸入了醫療隊的編號和他們之間相連接需要的條數

輸出指定的兩個醫療隊的最短路徑的條數,並且在最短路徑中能聚集的醫療隊的數量

例子:0到2的最短路徑可以是0-2.0-1-2.他們都是2的距離,但是0-1-2能聚集1+2+1的醫療隊,輸出4

 

用到深度優先算法:儘可能深的搜索,當節點所在的邊被探尋過或者不滿足條件時,回朔到上一步,反覆進行該過程直到所有的點遍歷

普適模板:

void dfs(int step):
{
    if 判斷邊界條件
    {
        
    }
    for 嘗試每一種可能
    {
         if判斷滿足條件
         標記
         繼續下一步的dfs
         恢復初始狀態
    }
}
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)] #橫縱座標爲兩個點,數值爲距離
visit = [0 for i in range(cities_num)] #訪問節點列表
min_roads = inf #最短路徑
min_roads_count = 0 #最短路徑條數
max_resue_sum =0 #最大救援隊個數

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): #如果小於當前的road數則更新
            min_roads_count = 1
            min_roads = road
            max_resue_sum = resue
        elif(road == min_roads):#如果等於則更新營救隊的最大個數
            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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