BFS

#include<stdio.h>
#include<queue>

using namespace std;
static const int N = 100;
static const int INFTY = (1 << 21);

int n, M[N][N];
int d[N];

void bfs(int s)
{
    queue<int> q;
    q.push(s);
    for (int i = 0;i < n;i++ )        d[i] = INFTY;
    d[s] = 0;                                //将第一个节点的距离定义为 0 
    int u;
    while( !q.empty() ) {                    //如果队列不为空 
        u = q.front() ;    q.pop() ;            //将队首取出 
        for ( int v = 0; v < n;v++ ){
            if ( M[u][v] == 0 || d[v] != INFTY)    continue;        //M为领接矩阵判断是否连通，d判断是否已遍历过 
            d[v] = d[u] + 1;                //d[u]为前一步的距离 
            q.push(v);                         //将新的节点放入队列 
        }
    }
}