41. First Missing Positive

class Solution {
    public int firstMissingPositive(int[] nums) {

        // 将 下标为 i 的位置对应放置数字大小为 i+1;
       int len = nums.length;
        for (int i = 0; i < len; i++) {
            while(nums[i] > 0 && nums[i] <= len
                    && nums[nums[i] - 1] != nums[i]) {
                swap(nums, i, nums[i] - 1);
            }
        }

　　　　// 查找
        for (int i = 0; i < len; i++) {
            if(nums[i] != i + 1)
                return i + 1;
        }
        return len + 1;
    }

    private void swap(int[] nums, int i, int j) {
        int tmp = nums[i];
        nums[i] = nums[j];
        nums[j] = tmp;
    }
}