Twitter OA prepare: Visit element of the array

分析：就是建立一个boolean array来记录array里面每个元素的访问情况，遇到访问过的元素就停止visiting，返回未访问的结点个数

public int visiting(int[] A, int N) {
    if (A==null || A.length==0) return 0;
    int cur = 0;
    int count = 0;
    boolean[] visited = new boolean[N];
    while (cur>=0 && cur<A.length && !visited[cur]) {
        visited[cur] = true;
        cur = cur + A[cur];
        count++;
    }
    return N-count;
}