Bellman Ford 的队列优化 (2) C~

此实现利用两个数组first[],  ext[] 邻接表。

核心代码：

void bellman_ford(int orig){int k;que[tail++] = orig;book[orig] = 1;while(head < tail){k = first[que[head]];while(k != -1){if(dist[edge[k].v] > dist[edge[k].u] + edge[k].w){dist[edge[k].v] = dist[edge[k].u] + edge[k].w;if(book[edge[k].v] == 0){que[tail++] = edge[k].v;book[edge[k].v] = 1;}}k = next[k];}book[que[head]] = 0;head++;}}

完整实现:

#include<stdio.h>#define INF 65535#define MAX 20typedef struct Edge{int u, v;int w;}Edge;int que[MAX] = {0};int head = 1, tail = 1;int next[MAX+1], first[MAX+1];int book[MAX];int dist[MAX];Edge edge[MAX];void bellman_ford(int orig){int k;que[tail++] = orig;book[orig] = 1;while(head < tail){//队列不空 就继续k = first[que[head]];//获取 当前顶点的 ’边‘ 的 序号while(k != -1){if(dist[edge[k].v] > dist[edge[k].u] + edge[k].w){dist[edge[k].v] = dist[edge[k].u] + edge[k].w;if(book[edge[k].v] == 0){que[tail++] = edge[k].v;book[edge[k].v] = 1;//入队后 标记}}k = next[k];}book[que[head]] = 0;// 出队 重新把标记置 0 意味着 可以重新 入队head++;}}int main(){int n, m;scanf("%d%d",&n,&m);for(int i = 1; i <= n; i++ ){//初始化book[i] = 0;first[i] = -1;next[i] = -1;dist[i] = INF;}int orig = 1;dist[orig] = 0;for(int j = 1; j <= m; j++ ){scanf("%d%d%d", &edge[j].u,&edge[j].v, &edge[j].w);//下面两句用数组模拟链表 next[j] = first[edge[j].u];first[edge[j].u] = j;}bellman_ford(orig);for(int i = 1; i <= n; i++ ){printf("%d ",dist[i]);}} 

模拟数组的方法讲解