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Solution.java
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Solution.java
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package g0001_0100.s0041_first_missing_positive;
// #Hard #Top_100_Liked_Questions #Top_Interview_Questions #Array #Hash_Table #Udemy_Arrays
// #Big_O_Time_O(n)_Space_O(n) #2023_08_11_Time_2_ms_(57.59%)_Space_59.2_MB_(51.48%)
public class Solution {
public int firstMissingPositive(int[] nums) {
for (int i = 0; i < nums.length; i++) {
if (nums[i] <= 0 || nums[i] > nums.length || nums[i] == i + 1) {
continue;
}
dfs(nums, nums[i]);
}
for (int i = 0; i < nums.length; i++) {
if (nums[i] != i + 1) {
return i + 1;
}
}
return nums.length + 1;
}
private void dfs(int[] nums, int val) {
if (val <= 0 || val > nums.length || val == nums[val - 1]) {
return;
}
int temp = nums[val - 1];
nums[val - 1] = val;
dfs(nums, temp);
}
}