THU-2016-3-1-TSP

描述

题解

代码

#include <cstdio>

#define MAX_N 100005
#define MAX_M 1000005
#define max(a, b) ((a > b) ? (a) : (b))

using namespace std;

const int INF = 0x3f3f3f3f;

struct edge
{
int to, w, next;
edge()
{
w = to = next = 0;
}
};

edge D[MAX_M];  //  邻接表
int head[MAX_N];//  邻接表头
int dp[MAX_M];  //  dp[i]:第i条边为开始的最长路
int num[MAX_N]; //  num[i]:以i为起点的最长路
int cnt = 1;

//  往邻接表中添加边
void add(int u, int v, int w)
{
D[cnt].to = v;
D[cnt].w = w;
D[cnt].next = head[u];
head[u] = cnt++;
}

//  树归部分
int DFS(int s)
{
int maxn = 0;
for (int i = head[s]; i; i = D[i].next)
{
if (dp[i] == -1)
{
dp[i] = DFS(D[i].to) + D[i].w;
}
maxn = max(maxn, dp[i]);
}
return maxn;
}

//  从起点开始查找最长路
void find(int s, int w)
{
printf("%d\t", s);
int minx = INF, W = 0;
for (int i = head[s]; i; i = D[i].next)
{
//  保证在最长路上并且字典序最小
if (dp[i] == w && minx > D[i].to)
{
W = w - D[i].w;
minx = D[i].to;
}
}
if (minx != INF)
{
find(minx, W);
}
return ;
}

int main()
{
int n, m;
scanf("%d%d", &n, &m);
for (int i = 0; i <= m; i++)
{
dp[i] = -1;
}

int a, b, p;
for (int i = 0; i < m; i++)
{
scanf("%d%d%d", &a, &b, &p);
add(a, b, p);
}

int maxn = -1, temp = 0;
for (int i = 1; i <= n; i++)
{
num[i] = DFS(i);
if (num[i] > maxn)
{
maxn = num[i];
temp = i;
}
}

find(temp, maxn);
printf("\n");

return 0;
}