【PAT A1018】Public Bike Management

题目太长就不抄了，这题得做个重点记号，比较典型。

#include <cstdio>
#include <vector>
#include <stack>
using namespace std;

int cMax, N, Sp, M, cap[510] = {0}, G[510][510] = {0}, visited[510] = {0};
int dis[510] = {0}, inf = 1000000000, give[510] = {0};
vector<int> fore[510], path ,ans;
int minCnt = inf, minTake = inf;

void dfs(int v){
	//已找到一条路径
	if(v == 0){
		path.push_back(v);
		//cnt为当前点多余的车，take记录要带的车
		int cnt = 0, take = 0;
		for(int i = path.size() - 1; i >= 0; i--){
			if(cnt + cap[path[i]] <= 0){
				take -= (cnt + cap[path[i]]);
				cnt = 0;
			}
			else
				cnt += cap[path[i]]; 
		}
		if(take < minTake){
			minTake = take;
			ans = path;
			minCnt = cnt;
		}
		else if(take == minTake && cnt < minCnt){
			ans = path;
			minCnt = cnt;
		}
		path.pop_back();
		return;
	}
	path.push_back(v);//将当前节点放到路径中
	for(int i = 0; i < fore[v].size(); i++)
		dfs(fore[v][i]);
	path.pop_back();//将当前节点从路径中去掉，找其他的路
}

int main(){
	scanf("%d%d%d%d", &cMax, &N, &Sp, &M);
	cMax /= 2;
	for(int i = 1; i <= N; i++){
		scanf("%d", &cap[i]);
		cap[i] -= cMax;
		dis[i] = inf;
	}
	for(int i = 0; i < M; i++){
		int f, t, w;
		scanf("%d%d%d", &f, &t, &w);
		G[f][t] = G[t][f] = w;
	}

	//dijkstra
	for(int i = 0; i <= N; i++){
		int index = -1, min = inf;
		for(int j = 0; j <= N; j++){
			if(visited[j] == 0 && dis[j] < min){
				index = j;
				min = dis[j];
			}
		}
		if(index == -1)
			break;
		visited[index] = 1;
		for(int j = 0; j <= N; j++){
			//printf("index is %d\n", index);
			if(G[index][j] != 0){
				if(dis[index] + G[index][j] < dis[j]){
					dis[j] = dis[index] + G[index][j];
					fore[j].clear();
					fore[j].push_back(index);
				}
				//cnt用来保存当前节点多余的bike
				else if(dis[index] + G[index][j] == dis[j]){
					fore[j].push_back(index);
				}
			}
		}
	}

	dfs(Sp);
	printf("%d ", minTake);
	for(int i = ans.size() - 1; i >= 0; i--){
		if(i > 0)
			printf("%d->", ans[i]);
		else
			printf("%d ", ans[i]);
	}
	printf("%d\n", minCnt);

	return 0;
}