poj 2387 Dijkstra入门（动态图解）

Til the Cows Come Home

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 43861		Accepted: 14902

Description

Bessie is out in the field and wants to get back to the barn to get as much sleep as possible before Farmer John wakes her for the morning milking. Bessie needs her beauty sleep, so she wants to get back as quickly as possible. 

Farmer John's field has N (2 <= N <= 1000) landmarks in it, uniquely numbered 1..N. Landmark 1 is the barn; the apple tree grove in which Bessie stands all day is landmark N. Cows travel in the field using T (1 <= T <= 2000) bidirectional cow-trails of various lengths between the landmarks. Bessie is not confident of her navigation ability, so she always stays on a trail from its start to its end once she starts it. 

Given the trails between the landmarks, determine the minimum distance Bessie must walk to get back to the barn. It is guaranteed that some such route exists.

Input

* Line 1: Two integers: T and N 

* Lines 2..T+1: Each line describes a trail as three space-separated integers. The first two integers are the landmarks between which the trail travels. The third integer is the length of the trail, range 1..100.

Output

* Line 1: A single integer, the minimum distance that Bessie must travel to get from landmark N to landmark 1.

Sample Input

5 5
1 2 20
2 3 30
3 4 20
4 5 20
1 5 100

Sample Output

90

Hint

INPUT DETAILS: 

There are five landmarks. 

OUTPUT DETAILS: 

Bessie can get home by following trails 4, 3, 2, and 1.

题意：就是给你 n  个岛屿，t  条路径

然后下面就是 t 行：每一行表示   从 某一个点到某一个点，并且给出距离

这个算法的动态图

#include
#include
#include
using namespace std;


const int maxx=1010;
const int INF=0x3f3f3f3f;


int map[maxx][maxx];//记录点到点
int path[maxx];//代表走到位置 i 需要最少走多远
int flag[maxx];//标记是否遍历过




//-----------查找没有被遍历过的最小路径---------//
int find_it(int n)
{
    int pos=-1,min=INF;
    for(int i=1;i<=n;i++){
        if(!flag[i]&&path[i]