我在Codility上遇到了一个非常奇怪的问题,这是任务描述:
Write a function:
class Solution { public int solution(int[] A); }
that, given a non-empty zero-indexed array A of N integers, returns the minimal positive integer that does not occur in A.
For example, given:
A[0] = 1
A[1] = 3
A[2] = 6
A[3] = 4
A[4] = 1
A[5] = 2
the function should return 5.
Assume that:
N is an integer within the range [1..100,000];
each element of array A is an integer within the range [−2,147,483,648..2,147,483,647].
Complexity:
expected worst-case time complexity is O(N);
expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).
Elements of input arrays can be modified.
以下是我的代码:
class Solution {
public int solution(int[] A) {
SortedSet set = new TreeSet();
for (int i = 0; i < A.length; i++)
if (A[i] > 0)
set.add(A[i]);
Iterator it = set.iterator();
int previous = 0, element = 0;
try { previous = (int)it.next(); }
catch (NoSuchElementException e) { return 1; }
while (it.hasNext()) {
element = (int)it.next();
if (element!=(previous+1)) break;
previous=element;
}
if (previous+1 < 1) return 1;
return previous+1;
}
}
代码分析:
http://i.stack.imgur.com/IlMxP.png
我试图弄清楚为什么我的代码只在那个测试中提供了错误的输出,有人能帮助我吗?
先谢谢了!
TreeSet
的插入时间,您的代码具有最坏的时间复杂度O(N*Log(N))。 - Sergey Kalinichenko