1150 Travelling Salesman Problem

1150 Travelling Salesman Problem
The “travelling salesman problem” asks the following question: “Given a list of cities and the distances between each pair of cities, what is the shortest possible route that visits each city and returns to the origin city?” It is an NP-hard problem in combinatorial optimization, important in operations research and theoretical computer science. (Quoted from “https://en.wikipedia.org/wiki/Travelling_salesman_problem”.)

In this problem, you are supposed to find, from a given list of cycles, the one that is the closest to the solution of a travelling salesman problem.

Input Specification:
Each input file contains one test case. For each case, the first line contains 2 positive integers N (2<N≤200), the number of cities, and M, the number of edges in an undirected graph. Then M lines follow, each describes an edge in the format City1 City2 Dist, where the cities are numbered from 1 to N and the distance Dist is positive and is no more than 100. The next line gives a positive integer K which is the number of paths, followed by K lines of paths, each in the format:

n C
​1
​​ C
​2
​​ … C
​n
​​

where n is the number of cities in the list, and C
​i
​​ 's are the cities on a path.

Output Specification:
For each path, print in a line Path X: TotalDist (Description) where X is the index (starting from 1) of that path, TotalDist its total distance (if this distance does not exist, output NA instead), and Description is one of the following:

TS simple cycle if it is a simple cycle that visits every city;
TS cycle if it is a cycle that visits every city, but not a simple cycle;
Not a TS cycle if it is NOT a cycle that visits every city.
Finally print in a line Shortest Dist(X) = TotalDist where X is the index of the cycle that is the closest to the solution of a travelling salesman problem, and TotalDist is its total distance. It is guaranteed that such a solution is unique.

Sample Input:
6 10
6 2 1
3 4 1
1 5 1
2 5 1
3 1 8
4 1 6
1 6 1
6 3 1
1 2 1
4 5 1
7
7 5 1 4 3 6 2 5
7 6 1 3 4 5 2 6
6 5 1 4 3 6 2
9 6 2 1 6 3 4 5 2 6
4 1 2 5 1
7 6 1 2 5 4 3 1
7 6 3 2 5 4 1 6
Sample Output:
Path 1: 11 (TS simple cycle)
Path 2: 13 (TS simple cycle)
Path 3: 10 (Not a TS cycle)
Path 4: 8 (TS cycle)
Path 5: 3 (Not a TS cycle)
Path 6: 13 (Not a TS cycle)
Path 7: NA (Not a TS cycle)
Shortest Dist(4) = 8
分析：现在有一无向图，给定顶点序列，计算顶点序列的长度，并且判断序列的性质。TS simple cycle，序列形成一个环，并且经过了所有顶点且每个顶点只经过一次；TS cycle 仅仅形成一个环；其余的情况则归为Not a TS cycle一类。
参考代码：

#include<iostream>
#include<set>
#include<vector>
#include<string>
#define N 205
using namespace std;

int graph[N][N];
int main() {
	int n,m, a, b, w, k, t, query, sum, flag = 1, min = 15984876, res,first;
	vector<string>v{ "TS simple cycle","TS cycle","Not a TS cycle" };
	scanf_s("%d%d", &n, &m);
	for (int i = 1; i <= m; i++) {
		scanf_s("%d%d%d", &a, &b, &w);
		graph[a][b] = w;
		graph[b][a] = w;
	}
	scanf_s("%d", &k);
	for (int i = 1; i <= k; i++) {
		scanf_s("%d", &t);
		set<int>s;
		sum = 0; flag = 1;
		for (int j = 1; j <= t; j++) {
			scanf_s("%d", &b);
			if (j == 1) { a = b; first = b; }
			else {
				if (flag) {
					if (graph[a][b] != 0)
						sum += graph[a][b];
					else flag = 0;
				}
				a = b;
			}
			s.insert(b);
		}
		if (flag&&s.size() == n && t == n + 1&&b==first)
			res = 0;
		else if (flag&&s.size() == n&&b==first)
			res = 1;
		else res = 2;
		if ((res == 0||res==1)&&sum<min){			
			min = sum;
			query = i;
		}
		printf("Path %d:", i);
		if (flag)printf(" %d ", sum);
		else printf(" NA ");
		cout << "(" << v[res] << ")" << endl;
	}
	cout << "Shortest Dist(" << query << ") = " << min << endl;

	return 0;
}