CCF 201712-4 90分

90分，不知道错在哪里了，dijkstra算法，用一个数组的d[i]表示以i点结尾的小路的长度，以i点为中心扩展时，若下一点为k，如果i->k是小路，则

d[j] = d[k]+M[k][j];dist[j] = min_ - pow(d[k], 2) + pow(d[j], 2);

否则直接加路径长度即可，同时把d[j]=0

#include <iostream>
#include <cstdio>
#include <climits>
#include <cmath>
#include <cstring>
#include <algorithm>
using namespace std;
const int INF = 100000000;
const int MAXN = 505;
int M[MAXN][MAXN];
int kind[MAXN][MAXN];
int dijkstra(int n)
{
	int flag[MAXN];
	long long dist[MAXN];
	int k;
	int d[MAXN];
	memset(flag, 0, sizeof(flag));
	memset(d, 0, sizeof(d));
	for (int i = 0; i < n; i++)
	{
		if (M[0][i] > 0)
		{
			if (kind[0][i] == 0)
				dist[i] = M[0][i];
			else
			{
				dist[i] = pow(M[0][i], 2);
				d[i] = M[0][i];
			}
		}
		else
			dist[i] = -1;

	}
	flag[0] = 1;
	dist[0] = 0;
	for (int i = 1; i < n; i++)
	{
		int min_ = INF;
		for (int j = 0; j < n; j++)
		{
			if (!flag[j]&&dist[j]>0&&dist[j]<min_)
			{
				min_ = dist[j];
				k = j;
			}
		}
		flag[k] = 1;
		for (int j = 0; j < n; j++)
		{
			if (!flag[j] && M[j][k]>0)
			{
				if (dist[j] < 0)
				{
					if (kind[k][j] == 0)
					{
						d[j] = 0;
						dist[j] = min_ + M[j][k];
					}
					else
					{
						d[j] = d[k]+M[j][k];
						dist[j] = min_ - pow(d[k], 2) + pow(d[k] + M[j][k],2);
					}
					continue;
				}
				if (dist[j] > 0)
				{
					if (kind[k][j] == 0)
					{
						if (dist[j] > min_ + M[j][k])
						{
							dist[j] = min_ + M[j][k];
							d[j] = 0;
						}
					}
					else
					{
						int temp = min_ - pow(d[k], 2) + pow(d[k] + M[k][j], 2);
						if (dist[j] > (min_ - pow(d[k], 2) + pow(d[k]+M[k][j], 2)))
						{
							d[j] = d[k]+M[k][j];
							dist[j] = min_ - pow(d[k], 2) + pow(d[j], 2);
						}
					}
					continue;
				}
			}
		}

	}
	return dist[n-1];
}
int main()
{
	int n, m;
	while (~scanf("%d %d",&n,&m))
	{
		for (int i = 0; i < n; i++)
			for (int j = 0; j < n; j++)
				if (i == j)M[i][j] = 0;
				else M[i][j] = -1;
		memset(kind, 0, sizeof(kind));
		for (int i = 0; i < m; i++)
		{
			int k, a, b, c;
			scanf("%d %d %d %d", &k, &a, &b, &c);
			M[a-1][b-1] = M[b-1][a-1] = c;
			kind[a-1][b-1] = kind[b-1][a-1] = k;
		}
		cout<<dijkstra(n)<<endl;

	}
	return 0;
}