最短路——SPFA

Bellman-Ford基础上的队列优化，效率比较高，可以检测负环。

const int maxn = 110;const int max_int = ~(1<<31);const int min_int = (1<<31);bool inq[maxn];int cost[maxn][maxn], dist[maxn], cnt[maxn], q[maxn], front, rear;//[0,max_int]int min(int a, int b){return a < b ? a : b;}int spfa(int s){memset(inq, 0, sizeof(inq));memset(cnt, 0, sizeof(cnt));for(int i = 0; i < n; ++i){dist[i] = max_int;}dist[s] = 0;front = rear = 0;q[rear++] = s;inq[s] = true;++cnt[s];while(front != rear){int now = q[front++];inq[now] = false;for(int i = 0; i < n; ++i)if(cost[now][i] != max_int && dist[i] > dist[now] + cost[now][i]){dist[i] = dist[i] + cost[now][i];if(!inq(i)){q[rear++] = i;inq[i] = true;++cnt[i];}if(cnt[i] > n){return -1;}}}}