[LeetCode] Longest Continuous Increasing Subsequence 最长连续递增序列

时间:2020-12-01 16:45:13

Given an unsorted array of integers, find the length of longest continuous increasing subsequence.

Example 1:

Input: [1,3,5,4,7]
Output: 3
Explanation: The longest continuous increasing subsequence is [1,3,5], its length is 3.
Even though [1,3,5,7] is also an increasing subsequence, it's not a continuous one where 5 and 7 are separated by 4.

Example 2:

Input: [2,2,2,2,2]
Output: 1
Explanation: The longest continuous increasing subsequence is [2], its length is 1.

Note: Length of the array will not exceed 10,000.

这道题让我们求一个数组的最长连续递增序列,由于有了连续这个条件,跟之前那道 Number of Longest Increasing Subsequence 比起来,其实难度就降低了很多。可以使用一个计数器,如果遇到大的数字,计数器自增1;如果是一个小的数字,则计数器重置为1。用一个变量 cur 来表示前一个数字,初始化为整型最大值,当前遍历到的数字 num 就和 cur 比较就行了,每次用 cnt 来更新结果 res,参见代码如下:

解法一:

class Solution {
public:
int findLengthOfLCIS(vector<int>& nums) {
int res = , cnt = , cur = INT_MAX;
for (int num : nums) {
if (num > cur) ++cnt;
else cnt = ;
res = max(res, cnt);
cur = num;
}
return res;
}
};

下面这种方法的思路和上面的解法一样,每次都和前面一个数字来比较,注意处理无法取到钱一个数字的情况,参见代码如下:

解法二:

class Solution {
public:
int findLengthOfLCIS(vector<int>& nums) {
int res = , cnt = , n = nums.size();
for (int i = ; i < n; ++i) {
if (i == || nums[i - ] < nums[i]) res = max(res, ++cnt);
else cnt = ;
}
return res;
}
};

Github 同步地址:

https://github.com/grandyang/leetcode/issues/674

类似题目:

Number of Longest Increasing Subsequence

Minimum Window Subsequence

参考资料:

https://leetcode.com/problems/longest-continuous-increasing-subsequence/

https://leetcode.com/problems/longest-continuous-increasing-subsequence/discuss/107352/Java-code-6-liner

https://leetcode.com/problems/longest-continuous-increasing-subsequence/discuss/107365/JavaC%2B%2BClean-solution

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