<p>Given an unsorted integer array <code>nums</code>. Return the <em>smallest positive integer</em> that is <em>not present</em> in <code>nums</code>.</p>

<p>You must implement an algorithm that runs in <code>O(n)</code> time and uses <code>O(1)</code> auxiliary space.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,0]
<strong>Output:</strong> 3
<strong>Explanation:</strong> The numbers in the range [1,2] are all in the array.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [3,4,-1,1]
<strong>Output:</strong> 2
<strong>Explanation:</strong> 1 is in the array but 2 is missing.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> nums = [7,8,9,11,12]
<strong>Output:</strong> 1
<strong>Explanation:</strong> The smallest positive integer 1 is missing.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>-2<sup>31</sup> &lt;= nums[i] &lt;= 2<sup>31</sup> - 1</code></li>
</ul>

int speedUp = []
{std::ios::sync_with_stdio(0); std::cin.tie(0); return 0; }();
bool has[100002];

int digit(char c)
{
    return c & 15;
}
bool isDigit(char c)
{
    return '0' <= c && c <= '9';
}
int init = [] {
    std::ofstream out("user.out");
    std::cout.rdbuf(out.rdbuf());
    for (string s; std::getline(std::cin, s); std::cout << '\n') {
        int n = count(s.begin(), s.end(), ',') + 3;
        memset(has, 0, n);
        for (int _i = 1, _n = s.length(); _i < _n; ++_i) {
            if (s[_i] == '-')for (_i += 2; isDigit(s[_i]); ++_i);
            else {
                int v = s[_i++] & 15;
                while (isDigit(s[_i])) v = v * 10 + digit(s[_i++]);
                if (0 < v && v < n) has[v] = true;
            }
        }
        for (int i = 1;; ++i)
            if (!has[i]) {
                std::cout << i;
                break;
            }
    }
    exit(0);
    return 0;
}();

class Solution {
public:
    int firstMissingPositive(vector<int>) { return 0; }
};
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