41 缺失的第一个正数

https://leetcode.cn/leetbook/read/top-interview-questions-hard/xwkftg/

cost: 16m13s

class Solution {
public:
    int firstMissingPositive(vector<int>& nums) {
        for (int i = 0; i < nums.size();) {
            int v = nums[i];
            if (v == i + 1) {
                i++;
                continue;
            }
            if (v < i + 1 && v >= 1) {
                if (nums[v - 1] == v) {
                    nums[i] = -1;
                    i++;
                    continue;
                }
                std::swap(nums[v - 1], nums[i]);
                i++;
                continue;
            }
            if (v > i + 1 && v - 1 < nums.size()) {
                if (nums[v - 1] == v) {
                    nums[i] = -1;
                    i++;
                    continue;
                }
                std::swap(nums[v - 1], nums[i]);
                continue;
            }
            nums[i] = -1;
            i++;
        }
        for (int i = 0; i < nums.size(); i++) {
            if (nums[i] == -1) {
                return i + 1;
            }
        }
        return nums.size() + 1;
    }
};