FirstMissingPositive.java

// First Missing Positive
// URL : https://leetcode.com/problems/first-missing-positive/

package com.akshat;

public class FirstMissingPositive {

 public static void main(String[] args) {

 int[] nums = {7, 8, 9, 11, 12};

 System.out.println(firstMissingPositive(nums));

 }

 static int firstMissingPositive(int[] nums){
 int i = 0;
 while (i < nums.length){
 int correct = nums[i] - 1;
 if (nums[i]>0 && nums[i]<=nums.length && nums[i]!=nums[correct]){
 swap(nums, i, correct);
 }
 else{
 i++;
 }
 }
 for (int index=0; index< nums.length; index++){
 if (nums[index] != index+1){
 return index+1;
 }
 }
 return nums.length+1;
 }

 static void swap(int[] nums, int first, int second){
 int temp = nums[first];
 nums[first] = nums[second];
 nums[second] = temp;
 }

}