[LintCode] Longest Increasing Continuous Subsequence 最长连续递增子序列

简介:

Give an integer array,find the longest increasing continuous subsequence in this array.

An increasing continuous subsequence:

  • Can be from right to left or from left to right.
  • Indices of the integers in the subsequence should be continuous.
 Notice

O(n) time and O(1) extra space.

Example

For [5, 4, 2, 1, 3], the LICS is [5, 4, 2, 1], return 4.

For [5, 1, 2, 3, 4], the LICS is [1, 2, 3, 4], return 4 

这道题跟LeetCode上那道Longest Increasing Subsequence很像,但是比那道题简单,因为这道题需要递增子序列连续,这样我们只要挨个比较一下即可,由于题目中说了左右两个方向递增都行,可以用左右两个方向分别遍历一遍,也可以把两个遍历合并到一起,只用一个循环,同时寻找递增和递减的数列,使用两个变量cnt1和cnt2分别记录最长递增和递减数列的长度,一旦递增递减断开,记得将对应的计数器重置即可,参见代码如下:

class Solution {
public:
    /**
     * @param A an array of Integer
     * @return  an integer
     */
    int longestIncreasingContinuousSubsequence(vector<int>& A) {
        if (A.empty()) return 0;
        int res = 1, cnt1 = 1, cnt2 = 1;
        for (int i = 0; i < A.size() - 1; ++i) {
            if (A[i] < A[i + 1]) {
                ++cnt1; 
                cnt2 = 1;
            } else {
                ++cnt2;
                cnt1 = 1;
            }
            res = max(res, max(cnt1, cnt2));
        }
        return res;
    }
};

本文转自博客园Grandyang的博客,原文链接:最长连续递增子序列[LintCode] Longest Increasing Continuous Subsequence ,如需转载请自行联系原博主。

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