Dijkstra algorithm.

/* As we all know that, in routing protocol OSPF, algorithm Dijkstra is used to calculate the shortest path. * The following codes show us the basic operation in Dijkstra. But there are still many faults. * For example, the "path" variable cannot shows us the vertex sequence and if there are more than one paths * which have the same cost, the variable "distance" can only show us the last one ...... * version: 0.1; by: double; date: 2009-07-12. */#include "/usr/c/head.h"#define MAX 20#define INT_MAX ((int)(~0U>>1))#define SCAN_INT(x, y); if (scanf("%d", &x) != EOF) while ((y = getchar()) != '/n' && y != EOF) {;}#define SCAN_CHAR(x, y); if (scanf("%c", &x) != EOF) while ((y = getchar()) != '/n' && y != EOF) {;}typedef int arc_type;typedef char vex_type;typedef struct matrix_graph {vex_type vexs[MAX];arc_type arcs[MAX][MAX];int vexnum, arcnum;}matrix_graph;matrix_graph G;int final[MAX];int distance[MAX];int path[MAX][MAX];int locate_vex(matrix_graph G, vex_type v) {int i;for (i = 0; i < G.vexnum; ++i)if (G.vexs[i] == v)return i;return -1;}status init_graph(matrix_graph *G) {int temp, i, j, p1, p2;vex_type v1, v2;printf("Input the vexnum:");SCAN_INT(G->vexnum, temp);for (i = 0; i < G->vexnum; ++i) {printf("No.%d:", i + 1);SCAN_CHAR(G->vexs[i], temp);for (j = 0; j < G->vexnum; ++j)G->arcs[i][j] = INT_MAX;}printf("Input the arcnum:");SCAN_INT(G->arcnum, temp);for (i = 0; i < G->arcnum; ++i) {printf("No.%d, v1:", i + 1);SCAN_CHAR(v1, temp);printf("No.%d, v2:", i + 1);SCAN_CHAR(v2, temp);p1 = locate_vex(*G, v1);if (p1 == -1) {printf("v1 = %c out of range!/n");exit(ERROR);}p2 = locate_vex(*G, v2);if (p2 == -1) {printf("v2 = %c out of range!/n");exit(ERROR);}printf("Weight:");SCAN_INT(G->arcs[p1][p2], temp);}return OK;}status print_graph(matrix_graph G) {int i, j;printf("vextex are:/n");for (i = 0; i < G.vexnum; ++i)printf("%c/t", G.vexs[i]);printf("arcs are:/n");for (i = 0; i < G.vexnum; ++i) {for (j = 0; j < G.vexnum; ++j)printf("%d/t", G.arcs[i][j]);printf("/n/n/n/n");}return OK;}status dijkstra(vex_type ch) {int k, i, w, j, min, v;k = locate_vex(G, ch);for (i = 0; i < G.vexnum; ++i) {distance[i] = G.arcs[k][i];final[i] = FALSE;for (w = 0; w < G.vexnum; ++w) path[k][w] = FALSE;if (distance[i] < INT_MAX) {path[i][i] = TRUE;path[i][k] = TRUE;}}distance[k] = 0;final[k] = TRUE;for (i = 1; i < G.vexnum; ++i) {min = INT_MAX;for (w = 0; w < G.vexnum; ++w)if (!final[w] && distance[w] < min) {v = w;min = distance[w];}final[v] = TRUE;for (w = 0; w < G.vexnum; ++w) if (!final[w] && min + G.arcs[v][w] > 0 && min + G.arcs[v][w] < distance[w]) {distance[w] = min + G.arcs[v][w];for (j = 0; j < G.vexnum; ++j) path[w][j] = path[v][j];path[w][w] = TRUE;}}return OK;}int main(void) {vex_type ch;int temp, i, j;init_graph(&G);printf("Graph initilized OK!/n");printf("Input the starting vertex:");SCAN_CHAR(ch, temp);dijkstra(ch);for (i = 0; i < G.vexnum; ++i)printf("%d/t", distance[i]);printf("/n/n");for (i = 0; i < G.vexnum; ++i) {for (j = 0; j < G.vexnum; ++j)printf("%3d", path[i][j]);printf("/n/n");}return 0;}