重复造轮子系列--dijkstra算法
前年一时脑热（理想很丰满，现实很骨感），写了这个最短路径优先的低效版本，且留着回忆吧。
spf.h
1 #ifndef SPF_H_ 2 #define SPF_H_ 3 4 5 typedef struct { 6 int length; 7 char src; 8 char dst; 9 char prev_hop; 10 } dijkstra; 11 12 #define MAX 1024 13 #define NODE_NUM 5 14 #define TRUE 1 15 #define FALSE 0 16 17 #endif
spf.c
1 #include <stdio.h> 2 #include <stdarg.h> 3 #include <string.h> 4 #include <limits.h> 5 #include <time.h> 6 #include <sys/timeb.h> 7 #include "spf.h" 8 9 dijkstra DIJK[NODE_NUM][NODE_NUM] = {0}; 10 char NODES[NODE_NUM] = {'A', 'B', 'C', 'D', 'E'}; 11 int P_NDS[NODE_NUM] = {0}; 12 int U_NDS[NODE_NUM] = {0}; 13 14 int distance(char src, char dst); 15 void debug(char* fmt,...); 16 void spf_dijkstra_init(); 17 void spf_show_dijkstra_matrix(int top); 18 dijkstra* spf_shortest_path_cost(char src, char dst); 19 void spf_main(int src_top); 20 int in_pnd_sets(char src); 21 void spf_pu_sets_init(); 22 int spf_find_candidate_node(int src_top, int top); 23 int spf_calc_next_hop(int src_top, int top, int min_idx); 24 void time_show(); 25 26 int main(int argc, char **argv) { 27 int i; 28 //time_show(); 29 spf_dijkstra_init(); 30 for (i=0; i<NODE_NUM; i++) { 31 spf_pu_sets_init(); 32 spf_main(i); 33 //spf_show_dijkstra_matrix(i); 34 } 35 //time_show(); 36 return 0; 37 } 38 39 void spf_pu_sets_init() { 40 memset(P_NDS, 0, sizeof(P_NDS)); 41 memset(U_NDS, 0, sizeof(U_NDS)); 42 } 43 44 void spf_main(int src_top) { 45 int top = src_top; 46 int min_node_id = -1; 47 int loop = 0; 48 49 if (top >= NODE_NUM || top < 0) { 50 debug("input error src_top = %d, input again plz \n"); 51 return; 52 } 53 54 P_NDS[top] = TRUE; 55 while(TRUE) { 56 if (loop == NODE_NUM) break; 57 loop++; 58 59 min_node_id = spf_find_candidate_node(src_top, top); 60 if (min_node_id == -1) continue; 61 top = spf_calc_next_hop(src_top, top, min_node_id); 62 if (top<0 || top>NODE_NUM) continue; 63 P_NDS[top] = TRUE; 64 } 65 return; 66 } 67 68 int spf_find_candidate_node(int src_top, int top) { 69 int min_idx = -1; 70 int min_cost = MAX; 71 72 for (int i=0; i<NODE_NUM; i++) { 73 if (TRUE == P_NDS[i]) continue; // 已经计算过路由的就不在计算 74 75 int d1 = distance(NODES[top], NODES[i]); 76 if (MAX == d1 || 0 == d1) continue; 77 78 U_NDS[i] = TRUE; 79 dijkstra* dij_dst = spf_shortest_path_cost(NODES[src_top], NODES[i]); 80 dijkstra* dij_hop = spf_shortest_path_cost(NODES[src_top], NODES[top]); 81 82 if (NULL == dij_dst || NULL == dij_hop) continue; 83 84 // 如果源顶点与当前节点的距离 > 源顶点与当前顶点的距离 + 当前顶点与当前节点的距离， 85 // 则设置当前顶点为当前节点的上一跳节点 86 // 'S' 表示没有设置过上一跳节点 87 if (dij_dst->length > d1+dij_hop->length || dij_dst->prev_hop == 'S') { 88 dij_dst->prev_hop = NODES[top]; 89 } 90 91 if (d1 < min_cost) { 92 min_cost = d1; 93 min_idx = i; 94 } 95 } 96 97 return min_idx; 98 } 99 100 int spf_calc_next_hop(int src_top, int top, int min_idx) { 101 for (int i=0; i<NODE_NUM; i++) { 102 if (FALSE == U_NDS[i]) continue; 103 int d1 = distance(NODES[src_top], NODES[i]); 104 int d2 = distance(NODES[top], NODES[i]); 105 106 if (0 == d2) continue; 107 dijkstra* dij_top = spf_shortest_path_cost(NODES[src_top], NODES[top]); 108 int d3 = d2 + dij_top->length; 109 dijkstra* dij_dst = spf_shortest_path_cost(NODES[src_top], NODES[i]); 110 if (!dij_dst) continue; 111 112 // 如果源顶点到当前节点的已经过计算的最短路径距离小于直接计算源顶点与当前节点距离 113 //，则使用最短路径距离 114 if (dij_dst->length < d1) d1 = dij_dst->length; 115 116 // 如果源顶点与当前顶点的距离+当前顶点到当前节点的距离 117 // 小于直接计算源顶点与当前节点距离， 118 // 则把当前顶点设置为当前的节点上一跳 119 if (0 < d3 && d3 < MAX && d3 <= d1) { 120 dij_dst->prev_hop = NODES[top]; 121 dij_dst->length = d3; 122 U_NDS[i] = FALSE; 123 } 124 // 如果当前节点的最短路径距离小于当前顶点计算的距离， 125 // 则调整当前节点上一跳，重新开始最短路由运算 126 else if (d1 > 0 && d1 < d3 && d3 < MAX) { 127 int d = distance(dij_dst->src, dij_dst->dst); 128 // 如果源顶点与目标节点是直连，并且距离小于最短路径距离， 129 // 则设置上一条节点为源顶点 130 if (MAX!=d && d<dij_dst->length) 131 dij_dst->prev_hop = dij_dst->src; 132 133 P_NDS[top] = FALSE; 134 U_NDS[top] = TRUE; 135 min_idx = i; 136 } 137 } 138 return min_idx; 139 } 140 141 int in_pnd_sets(char src) { 142 int i; 143 for (i=0; i<NODE_NUM; i++) 144 if (NODES[i] == src && P_NDS[i] == TRUE) 145 return TRUE; 146 return FALSE; 147 } 148 149 void spf_dijkstra_init() { 150 int i,j; 151 for (i=0; i<NODE_NUM; i++) { 152 for (j=0; j<NODE_NUM; j++) { 153 DIJK[i][j].length = distance(NODES[i], NODES[j]); 154 DIJK[i][j].src = NODES[i]; 155 DIJK[i][j].dst = NODES[j]; 156 DIJK[i][j].prev_hop = DIJK[i][j].length == 0 ? NODES[i] : 'S'; 157 } 158 } 159 return; 160 } 161 162 void spf_show_dijkstra_matrix(int top) { 163 int i,j; 164 for (i=0; i<NODE_NUM; i++) { 165 for (j=0; j<NODE_NUM; j++) { 166 if (top == i && DIJK[i][j].src != DIJK[i][j].dst) 167 printf("len=%d src=%c dst=%c prev=%c\n", 168 DIJK[i][j].length, DIJK[i][j].src, 169 DIJK[i][j].dst, DIJK[i][j].prev_hop); 170 } 171 } 172 printf("\n"); 173 return; 174 } 175 176 dijkstra* spf_shortest_path_cost(char src, char dst) { 177 dijkstra* dij = &DIJK[0][0]; 178 for (int k=0; k<NODE_NUM*NODE_NUM; k++,dij++) { 179 if (dij->src == src && dij->dst == dst) 180 return dij; 181 } 182 183 return NULL; 184 } 185 186 int distance(char src, char dst) { 187 if (src == dst) return 0; 188 if ('A' == src && 'B' == dst) return 1; 189 if ('B' == src && 'A' == dst) return 1; 190 if ('A' == src && 'C' == dst) return 5; 191 if ('C' == src && 'A' == dst) return 5; 192 if ('B' == src && 'D' == dst) return 6; 193 if ('D' == src && 'B' == dst) return 6; 194 if ('B' == src && 'E' == dst) return 2; 195 if ('E' == src && 'B' == dst) return 2; 196 if ('C' == src && 'E' == dst) return 1; 197 if ('E' == src && 'C' == dst) return 1; 198 if ('D' == src && 'E' == dst) return 1; 199 if ('E' == src && 'D' == dst) return 1; 200 return MAX; 201 }
