Blue Bridge Cup Training Shortest path (SPFA template vector)

algorithm Training Shortest Path
time limit: 1.0s memory limit: 256.0MB

Problem Description

Given an n vertex, the forward graph of the M-Edge (some of which may be negative, but no negative ring is guaranteed). Please calculate the shortest path from point 1th to other points (vertices are numbered from 1 to n).

Input format

First line two integers n, M.
The next M-line, each line has three integers u, V, L, indicating that u to V has an edge of length L.

Output format

A total of n-1 lines, line I represents the shortest path from point No. 1th to I+1.

Sample input

3 3
1 2-1
2 3-1
3 1 2

Sample output

-1
-2

Data size and conventions

For 10% of data, n = 2,m = 2.

For 30% of data, n <= 5,m <= 10.

For 100% of data, 1 <= n <= 20000,1 <= m <= 200000,-10000 <= L <= 10000, guaranteeing that all vertices can be reached from any vertex.

Title Link: http://lx.lanqiao.org/problem.page?gpid=T15

Title Analysis: Remember SPFA's vector version of the board

#include <cstdio> #include <cstring> #include <queue> #include <vector>using namespace Std;int    Const MAX = 200005;int Const INF = 1 << 30;int n, m;struct edge{int u, v; int Val;}    E[max << 2];struct node{int V, W;        NODE (int vv, int ww) {v = vv;    W = ww;    }};vector <NODE> vt[max];int dis[max];bool vis[max];void spfa (int v0) {memset (Vis, false, sizeof (VIS));    for (int i = 1; I <= n; i++) dis[i] = INF;    Dis[v0] = 0;    Queue <int> q;    Q.push (V0);        while (!q.empty ()) {int u = q.front ();        Q.pop ();        Vis[u] = false;        int sz = Vt[u].size ();            for (int i = 0; i < sz; i++) {int v = VT[U][I].V;            int w = VT[U][I].W;                if (Dis[v] > Dis[u] + W) {Dis[v] = Dis[u] + W;                    if (!vis[v]) {Q.push (v);                VIS[V] = true;     }            }   }}}int Main () {scanf ("%d%d", &n, &m);    for (int i = 0; i < m; i++) scanf ("%d%d%d", &e[i].u, &AMP;E[I].V, &e[i].val);    for (int i = 0; i < m; i++) Vt[e[i].u].push_back (NODE (E[I].V, e[i].val));    SPFA (1); for (int i = 2; I <= n; i++) printf ("%d\n", Dis[i]);}

Blue Bridge Cup Training Shortest path (SPFA template vector)