LeetCode-in-Java
3201. Find the Maximum Length of Valid Subsequence I
Medium
You are given an integer array nums.
A subsequence sub of nums with length x is called valid if it satisfies:
(sub[0] + sub[1]) % 2 == (sub[1] + sub[2]) % 2 == ... == (sub[x - 2] + sub[x - 1]) % 2.
Return the length of the longest valid subsequence of nums.
A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
Example 1:
Input: nums = [1,2,3,4]
Output: 4
Explanation:
The longest valid subsequence is [1, 2, 3, 4].
Example 2:
Input: nums = [1,2,1,1,2,1,2]
Output: 6
Explanation:
The longest valid subsequence is [1, 2, 1, 2, 1, 2].
Example 3:
Input: nums = [1,3]
Output: 2
Explanation:
The longest valid subsequence is [1, 3].
Constraints:
2 <= nums.length <= 2 * 1051 <= nums[i] <= 107
Solution
public class Solution {
public int maximumLength(int[] nums) {
int n = nums.length;
int alter = 1;
int odd = 0;
int even = 0;
if (nums[0] % 2 == 0) {
even++;
} else {
odd++;
}
boolean lastodd = nums[0] % 2 != 0;
for (int i = 1; i < n; i++) {
boolean flag = nums[i] % 2 == 0;
if (flag) {
if (lastodd) {
alter++;
lastodd = false;
}
even++;
} else {
if (!lastodd) {
alter++;
lastodd = true;
}
odd++;
}
}
return Math.max(alter, Math.max(odd, even));
}
}