每日一题（PTA Advanced1003）：Emergency-dfs

我的代码：

#include<bits/stdc++.h>
using namespace std;
 
int main(){
    int num_city;
    int num_road;
    int start;
    int end;
    int Max=-1;
    cin>>num_city>>num_road>>start>>end;
    vector<int> is_vis(num_city,0);
    vector<int> aid(num_city);
    for(int i=0;i<num_city;i++){
        cin>>aid[i];
    }
    int x,y,dis;
    vector<vector<int>>path (num_road,vector<int>(num_road,0));
    for(int i=0;i<num_road;i++){
        cin>>x>>y>>dis;
        path[x][y]=path[y][x]=dis;
    }
    int shortest_path=99999999;
    int res_num=0;
    //int res_sum=0;
    function<void(int ,int,int)> dfs = [&](int node,int length,int sum) {
        if(length>shortest_path) return;
        if(node==end){
            if(length ==shortest_path){res_num++;Max=max(sum,Max);}
            if(length<shortest_path) {res_num=1;shortest_path=length;Max=sum;}
            return;
        }
        for(int i=0;i<num_city;i++){
                if(is_vis[i]==0 && path[i][node]!=0){
                    is_vis[i]=1;
                    dfs(i,length+path[i][node],sum+aid[i]);
                    is_vis[i]=0;
                }
            }
    };
    is_vis[start]=1;
    dfs(start,0,aid[start]);
    cout<<res_num<<" "<<Max;
    return 0;
}

佬的代码：

#include<bits/stdc++.h>
using namespace std;
 
const int MAX_LEN = 0x3f3f3f3f; 
const int c_maxn = 500+10;
int G[c_maxn][c_maxn];	//城市地图 
int c_pro[c_maxn];		//每个城市的救火队数量
int vis[c_maxn];		//-1为有回路、0为正在访问、1为已访问 
int c_n, r_n, sta, fin; 	//城市数量，道路数量，起点、终点 
 
int Min=MAX_LEN, Max = -1, num_r = 0;		//最优路程和救火队数量 
 
 
void dfs(int u, int len, int value) {
	if(len > Min) return;	//剪枝 
	if(u == fin) {
		if(Min > len) {		//如果路程更短，则直接更新 
			Min = len; Max = value;
			num_r = 1;
		} else if(Min == len) {	//如果路程相等，则比较救火队数量 
			Max = max(value, Max);
			num_r++;
		}
		return;
	}
	for(int v = 0; v < c_n; v++) {
		if(G[u][v] != -1) {
			if(vis[v] == 1) continue;
			vis[v] = 1;
			dfs(v, len+G[u][v], value+c_pro[v]);
			vis[v] = 0;
		}
//		cout << u << ' ' << v << ' ' << G[u][v] << '\n';
	} 
}
 
int main() {
	memset(G, -1, sizeof(G));
	cin >> c_n >> r_n >> sta >> fin;
	for(int i = 0; i < c_n; i++) cin >> c_pro[i];
	for(int i = 0; i < r_n; i++) {
		int x1, x2, v;
		cin >> x1 >> x2 >> v;
		G[x1][x2] = G[x2][x1] = v;
	}
	
	vis[sta] = 1;
	dfs(sta, 0, c_pro[sta]);	//起始节点、道路长度、起始救火队数量 
	cout << num_r << ' ' << Max << '\n';
	return 0;
}