public static boolean quickSearch(int a[], int x) {
    boolean f = false;
    int length = a.length;
    int i;
    for (i = 0; i < length - 1; i++) {
      if (x == a[i]) {
        f = true;
        break;
      }
    }
    return f;
}

// 二分法方法一
public static boolean erFen(int a[], int low, int high, int x) {
    boolean f = false;
    if (low <= high) {
      if (x < a[(low + high) / 2]) {
        f = erFen(a, low, (low + high) / 2 - 1, x);
      } else if (x > a[(low + high) / 2]) {
        f = erFen(a, (low + high) / 2 + 1, high, x);
      } else if (x == a[(low + high) / 2]) {
        f = true;
      }
    }
    return f;
}
// 二分法方法二
public static boolean erFen2(int a[], int x) {
    boolean f = false;
    int length = a.length;
    int low = 0;
    int high = length - 1;
    int mid;
    while (low <= high) {
      mid = a[(low + high) / 2];
      if (mid < x)
        low = (low + high) / 2 + 1;
      else if (mid > x)
        high = (low + high) / 2 - 1;
      else if (mid == x) {
        f = true;
        break;
      }
    }
    return f;
}