https://leetcode.com/problems/first-missing-positive/
Given an unsorted integer array, find the smallest missing positive integer.
Example 1:
Input: [1,2,0] Output: 3
Example 2:
Input: [3,4,-1,1] Output: 2
Example 3:
Input: [7,8,9,11,12] Output: 1
Note:
Your algorithm should run in O(n) time and uses constant extra space.
代码：
class Solution {
public:
int firstMissingPositive(vector<int>& nums) {
sort(nums.begin(), nums.end());
int n = nums.size();
int temp = n + 1;
for(int i = 0; i < n; i ++) {
if(nums[i] >= 0) {
temp = i;
break;
}
}
if(temp == n + 1) return 1;
else {
map<int, int> mp;
for(int i = temp; i < n; i ++)
mp[nums[i]] ++;
for(int i = 1; i <= nums[n - 1]; i ++) {
if(mp[i] == 0)
return i;
}
return nums[n - 1] + 1;
}
}
};