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Commit cc7ce3d

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solve first missing positive
1 parent 7098087 commit cc7ce3d

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2 files changed

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‎algs/0041.first_missing_positive.go‎

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package algs
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// FirstMissingPositive
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//
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// Given an unsorted integer array nums. Return the smallest positive integer that is not present in nums.
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//
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// You must implement an algorithm that runs in O(n) time and uses O(1) auxiliary space.
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//
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// Example 1:
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//
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// Input: nums = [1,2,0]
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// Output: 3
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// Explanation: The numbers in the range [1,2] are all in the array.
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//
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// Example 2:
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//
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// Input: nums = [3,4,-1,1]
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// Output: 2
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// Explanation: 1 is in the array but 2 is missing.
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//
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// Example 3:
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//
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// Input: nums = [7,8,9,11,12]
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// Output: 1
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// Explanation: The smallest positive integer 1 is missing.
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//
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// Constraints:
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//
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// 1 <= nums.length <= 10^5
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// -2^31 <= nums[i] <= 2^31 - 1
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func FirstMissingPositive(nums []int) int {
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for i := 0; i < len(nums); i++ {
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if nums[i] == 0 {
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nums[i] = -1
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}
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}
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for i := 0; i < len(nums); i++ {
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for nums[i] >= 1 && nums[i] <= len(nums) {
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j := nums[i] - 1
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tmp := nums[j]
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nums[j] = 0
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if i != j {
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if tmp != 0 {
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nums[i] = tmp
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} else {
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nums[i] = -1
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}
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}
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}
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}
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for i := 0; i < len(nums); i++ {
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if nums[i] != 0 {
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return i + 1
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}
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}
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return len(nums) + 1
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}

‎src/solution.rs‎

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@@ -873,4 +873,63 @@ impl Solution {
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}
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result
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}
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/// [41. Frist Missing Positive]
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///
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/// Given an unsorted integer array nums. Return the smallest positive integer that is not present in nums.
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///
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/// You must implement an algorithm that runs in O(n) time and uses O(1) auxiliary space.
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///
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/// Example 1:
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///
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/// Input: nums = [1,2,0]
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/// Output: 3
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/// Explanation: The numbers in the range [1,2] are all in the array.
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///
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/// Example 2:
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///
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/// Input: nums = [3,4,-1,1]
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/// Output: 2
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/// Explanation: 1 is in the array but 2 is missing.
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///
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/// Example 3:
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///
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/// Input: nums = [7,8,9,11,12]
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/// Output: 1
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/// Explanation: The smallest positive integer 1 is missing.
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///
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/// Constraints:
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///
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/// 1 <= nums.length <= 10^5
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/// -2^31 <= nums[i] <= 2^31 - 1
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pub fn first_missing_positive(mut nums: Vec<i32>) -> i32 {
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for i in 0..nums.len() {
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if nums[i] == 0 {
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nums[i] = -1;
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}
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}
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for i in 0..nums.len() {
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while nums[i] >= 1 && nums[i] <= nums.len() as i32 {
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let j = nums[i] as usize - 1;
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let tmp = nums[j];
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nums[j] = 0;
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if j == i {
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break;
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}
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if tmp != 0 {
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nums[i] = tmp;
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} else {
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nums[i] = -1;
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}
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}
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}
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for (i, &num) in nums.iter().enumerate() {
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if num != 0 {
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return i as i32 + 1;
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}
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}
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nums.len() as i32 + 1
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}
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}

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