图论入门编程

卡码网刷题链接：98. 所有可达路径

一、题目简述

二、编程demo

方法①邻接矩阵

from collections import defaultdict
#简历邻接矩阵
def build_graph(): 
    n, m = map(int,input().split()) 
    graph = [[0 for _ in range(n+1)] for _ in range(n+1)]
    for _ in range(m): 
        i,j = map(int,input().split()) 
        graph[i][j] = 1
    return graph,n
#深度优先搜索
def dfs(g,r,i,end,path):
    if i == end:
        r.append(path.copy())
        return 
    for k in range(1,end+1):
        if g[i][k]:
            path.append(k)
            dfs(g,r,k,end,path)
            path.pop()
    return 
#主函数
def main():
    graph,n = build_graph()
    result = []
    path = [1]
    dfs(graph,result,1,n,path)
    #按格式打印输出
    if not result:
        print(-1)
    for p in result:
        print(" ".join(map(str,p)))
    return 
if __name__ == "__main__":
    main()

方法②邻接表

from collections import defaultdict
def build_graph(): 
    n, m = map(int,input().split()) 
    graph = defaultdict(list) 
    for _ in range(m): 
        i,j = map(int,input().split()) 
        graph[i].append(j)
    return graph,n

def dfs(g,r,i,end,path):
    if i == end:
        r.append(path.copy())
        return 
    for k in g[i]:
        path.append(k)
        dfs(g,r,k,end,path)
        path.pop()
    return 

def main():
    graph,n = build_graph()
    result = []
    path = [1]
    dfs(graph,result,1,n,path)
    if not result:
        print(-1)
    for p in result:
        print(" ".join(map(str,p)))
    return 
if __name__ == "__main__":
    main()