[Oracle] LeetCode 41 First Missing Positive 思维

Given an unsorted integer array nums, return the smallest missing positive integer.

You must implement an algorithm that runs in \(O(n)\) time and uses constant extra space.

Solution

对于 \(nums[i]\) 它对应的位置应该是 \(nums[nums[i]-1]\)

点击查看代码

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