牛客网：缺失的第一个正整数

import java.util.HashMap;
import java.util.Map;

/**
 * @author xienl
 * @description 缺失的第一个正整数
 * @date 2022/7/5
 */

public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        int[] arr = {1, 0, 2};
        System.out.println(solution.minNumberDisappeared(arr));
    }

    public int minNumberDisappeared (int[] nums) {
        // write code here
        int n = nums.length;
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++){
            if (nums[i] > 0){
                map.put(nums[i], 1);
            }
        }
        int res = 1;
        for(int i = 0; i < map.size(); i++){
            if (!map.containsKey(res)){
                return res;
            }
            res++;
        }
        return res;
    }
}