【LeetCode算法练习（C++）】First Missing Positive

题目：
Given an unsorted integer array, find the first missing positive integer.
For example,
Given [1,2,0] return 3,
and [3,4,-1,1] return 2.
Your algorithm should run in O(n) time and uses constant space.

链接：First Missing Positive

解法：打表，将出现的正数在表中置0，遍历列表返回第一个非0的序号。时间O(n)

class Solution {public:    int firstMissingPositive(vector<int>& nums) {        vector<int> tmp;        int len = nums.size();        if (len == 0) return 1;        for (int i = 0; i <= len; i++) {            tmp.push_back(i);        }        for (int i = 0; i < len; i++) {            if (nums[i] > 0 && nums[i] <= len) tmp[nums[i]] = 0;        }        for (int i = 0; i <= len; i++) {            if (tmp[i]) return i;        }        return len + 1;    }};

Runtime: 3 ms