LeetCode : 41. First Missing Positive

[congr]

https://leetcode.com/problems/first-missing-positive/description/

[congr]

Hard.

https://leetcode.com/problems/first-missing-positive/discuss/17083/O(1)-space-Java-Solution

[congr]

class Solution {
    // 0 1 2 3 
    // 1 2 3 4
    public int firstMissingPositive(int[] nums) {
        int N = nums.length;
        for (int i = 0; i < nums.length; ) {
            if (nums[i] == i+1) i++; // nums = {1 2 3 4}
            else {
                int ind = nums[i]-1;
                if (ind >= 0 && ind < N && nums[ind] != nums[i]) swap (nums, ind, i);
                else i++;
            }
            System.out.println("i:" + i + " " + Arrays.toString(nums));
        }

        for (int i = 0; i < nums.length; i++) {
            if (nums[i] != i+1) return i+1;
        }

        return nums.length+1; // !!!
    }

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

Your input
[1,2,0]
Your stdout
i:1 [1, 2, 0]
i:2 [1, 2, 0]
i:3 [1, 2, 0]
Your answer
3
Expected answer
3

Your input
[3,4,-1,1]
Your stdout
i:0 [-1, 4, 3, 1]
i:1 [-1, 4, 3, 1]
i:1 [-1, 1, 3, 4]
i:1 [1, -1, 3, 4]
i:2 [1, -1, 3, 4]
i:3 [1, -1, 3, 4]
i:4 [1, -1, 3, 4]
Your answer
2
Expected answer
2