Php implementation of single-stream shortest path (dijkstra algorithm)

The single-source shortest path (dijkstra algorithm) php implements a medical project, in which the single-source shortest path algorithm is used in case scoring. The idea of dijkstra algorithm for single-source shortest path is as follows: if there is a shortest path from I to j (Vi ..... vk, Vj), Vk is a vertex before Vj. Then (Vi... Vk) must be the shortest path from I to k. Dijkstra is an algorithm that increases the length of the shortest path and generates the shortest path one by one. For example, php implementation of single-source shortest path (dijkstra algorithm)
In a medical project, the single-source shortest path algorithm is used in case scoring. The single-source shortest path dijkstra algorithm has the following ideas:
If there is a shortest path (Vi... Vk, Vj) from I to j, Vk is a vertex before Vj. Then (Vi... Vk) must be the shortest path from I to k. Dijkstra is an algorithm that increases the length of the shortest path and generates the shortest path one by one. For example, for the source vertex V0, first select its directly adjacent vertex Vi with the shortest length, the shortest distance from V0 to Vj vertex is known as dist [j] = min {dist [j], dist [I] + cost [I] [j]}. Suppose G = The source vertex is V0, U = {V0} indicates the vertex set that has been marked. dist [I] records the shortest distance from V0 to I, cost [I] [j] indicates the overhead from edge I to j.
1. select vertex I that minimizes dist [I] value from the V-U and add I to U;

2. Update The dist value of the vertex directly adjacent to I. (Dist [j] = min {dist [j], dist [I] + cost [I] [j]})

3. know U = V, stop.

The code of php is as follows:

Function dijkstra () {$ node_info_arr = array (// array of the adjacent table structure of the node ('node _ id' => 0, // id of a node 'next _ node' => array (, 1), 'node _ type' => 0, 'cost' => array, 100), array ('node _ id' => 4, // The id of a node 'next _ node' => array (3 ), 'node _ type' => 1, 'cost' => array (50), array ('node _ id' => 3, // id of a node 'next _ node' => array (1), 'node _ type' => 1, 'cost' => array (10 )), array ('node _ id' => 2, // id of a node 'next _ node' => array (3, 1), 'node _ type' => 1, 'cost' => array (60, 60) ), Array ('node _ id' => 1, // The id of a node 'next _ node' => array (), 'node _ type' => 2, 'cost' => array (); $ start_node_id = false; // start node id $ I _cost = array ()); // overhead between two nodes $ I _dist = array (); // The shortest distance from the start point to each point $ B _mark = array (); // whether foreach ($ node_info_arr as & $ node_info) {if ($ node_info ['node _ type'] = 0) is added) {$ start_node_id = $ node_info ['node _ id']; // locate the initial node} foreach ($ node_info ['next _ node'] as $ key => $ next_node) {$ I _cost [$ node_info ['node _ id'] [$ Next_node] = $ node_info ['cost'] [$ key];} $ I _dist [$ node_info ['node _ id'] = 'inf '; // The initialization is infinite $ B _mark [$ node_info ['node _ id'] = false; // initialization is not added} if ($ start_node_id = false) {return '000000';} // calculate the shortest path from the initial node to each node $ I _dist [$ start_node_id] = 0; // The distance between the initial vertex and its own is 0 $ B _mark [$ start_node_id] = true; // add the set $ current_node_id = $ start_node_id to the initial vertex; // recently added node id $ node_count = count ($ node_info_arr); for ($ I = 0; $ I <$ node_count; $ I ++) {$ min = 'inf '; // the closest distance to the current node if (is _ Array ($ I _cost [$ current_node_id]) {foreach ($ I _cost [$ current_node_id] as $ key => $ val) {if ($ I _dist [$ key] = 'inf '| $ I _dist [$ key]> $ I _dist [$ current_node_id] + $ val) {$ I _dist [$ key] = $ I _dist [$ current_node_id] + $ val ;}} foreach ($ I _dist as $ key => $ val) {if (! $ B _mark [$ key]) {if ($ val! = 'Inf '& ($ min = 'inf' | $ min> $ val) {$ min = $ val; $ candidate_node_id = $ key; // candidate latest node id }}if ($ min = 'inf ') {break;} $ current_node_id = $ candidate_node_id; $ B _mark [$ current_node_id] = true ;} foreach ($ I _dist as $ key => $ val) {echo $ start_node_id. '=> '. $ key. ':'. $ val.'
';}}

The example is an image:

The running result is:
0 => 0: 0
0 => 4: 10
0 => 3: 60
0 => 2: 30
0 => 1: 70