LeetCode 41 First Missing Positive

Given an unsorted integer array, find the first missing positive integer.

For example,
Given [1,2,0] return 3,
and [3,4,-1,1] return 2.

Your algorithm should run in O(n) time and uses constant space.

有点儿桶排序的思想了。

Runtime: 13 ms beats 48.07% of java submissions.

	public int firstMissingPositive(int[] nums) {
		for (int i = 0; i < nums.length; i++) {
			if (nums[i] > 0 && nums[i] != i + 1 && nums[i] < nums.length
					&& nums[nums[i] - 1] != nums[i]) {
				int tmp = nums[nums[i] - 1];
				nums[nums[i] - 1] = nums[i];
				nums[i--] = tmp;
			}
		}
		for (int i = 0; i < nums.length; i++) {
			if (nums[i] != i + 1) return i + 1;
		}
		return nums.length + 1;
	}