package top100liked

import "testing"

// https://leetcode.cn/problems/first-missing-positive/description/?envType=study-plan-v2&envId=top-100-liked

func firstMissingPositive(nums []int) int {
	n := len(nums)
	for i := range nums {
		for nums[i] >= 1 && nums[i] <= n && nums[i] != i+1 {
			if nums[i] != nums[nums[i]-1] { // 关键条件，否则会死循环 [1, 1]
				nums[i], nums[nums[i]-1] = nums[nums[i]-1], nums[i]
			} else {
				break
			}
		}
	}
	for i, v := range nums {
		if v != i+1 {
			return i + 1
		}
	}
	return n + 1
}

func TestS17(t *testing.T) {
	// println(firstMissingPositive([]int{1, 2, 0}))
	// println(firstMissingPositive([]int{3, 4, -1, 1}))
	// println(firstMissingPositive([]int{7, 8, 9, 11, 12}))
	println(firstMissingPositive([]int{1, 1}))
}