dfs

let dfs mat start finish =
        let n = Array.length mat in
        let visited = Array.make n 0 in
        let lista = ref [start] in
        let flague = ref false in
        while (!lista <> [] && !flague <> true)
        do
                let cur= List.hd !lista in
                lista:= List.tl !lista;
                for i = 0 to n-1 do
                        if(mat.(cur).(i)=1 && visited.(i)=0) then
                                if i=finish then (flague:=true;)
                                else
                                (visited.(i)<-1;
                                lista:=i::!lista;)
                done;
        done;
!flague