1. 题目

读题

考查点

2. 解法

思路

代码逻辑

具体实现

解法一：

public class Solution {

    public static void main(String[] args) {
        System.out.println(solution(new int[]{1, 3, 6, 4, 1, 2}));
        System.out.println(solution(new int[]{1, 2, 3}));
        System.out.println(solution(new int[]{-1,-3}));
    }


    public static int solution(int[] A) {
        for (int i = 1; i < Integer.MAX_VALUE; i++) {
            if (!contain(A, i)) {
                return i;
            }
        }
        return -1;
    }

    public static boolean contain(int[] nums, int n) {
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] == n) {
                return true;
            }
        }
        return false;
    }

}

解法二：

public class Solution2 {
    public static void main(String[] args) {
        System.out.println(solution(new int[]{1, 3, 6, 4, 1, 2}));
        System.out.println(solution(new int[]{1, 2, 3}));
        System.out.println(solution(new int[]{-1, -3}));
    }


    public static int solution(int[] A) {
        Arrays.sort(A);

        int n = A.length;

        if (A[n - 1] < 0) {
            return 1;
        }

        int index = 1;
        for (int i = 0; i < n; i++) {
            if (A[i] <= 0 || (i > 0 && A[i] == A[i - 1])) {
                continue;
            }
            if (A[i] == index) {
                index++;
            } else {
                return index;
            }

        }
        return index;
    }

}

3. 总结