397. Longest Continuous Increasing Subsequence

Posted 2020-12-04 phdeblog

Description

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.

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.

解题：记录连续增大或者连续减少的个数，返回最大值。代码如下：

public class Solution {
    /**
     * @param A: An array of Integer
     * @return: an integer
     */
    public int longestIncreasingContinuousSubsequence(int[] A) {
        // write your code here
        int i_count = 1;//上升的时候的个数
        int d_count = 1;//下降时候的个数
        int temp = 1;
        //注意，当下标有减号时，要注意返回，下标不为负
        if(A.length == 0){
            return 0;
        }
        for(int i = 1; i < A.length; i++){
            if(A[i] > A[i-1]){
                //说明增大
                temp++;
            }else{
                //否则
                if(temp > i_count){
                    i_count = temp;//更新
                }
                temp = 1;
            }
        }
        if(temp > i_count){
            //如果一直到最后，可能缺少一次跟新
            i_count = temp;
        }
        temp = 1;
        for(int i = 1; i < A.length; i++){
            if(A[i] < A[i-1]){
                //说明减小
                temp++;
            }else{
                //否则
                if(temp > d_count){
                    d_count = temp;//更新
                }
                temp = 1;
            }
        }
        if(temp > d_count){
            //如果一直到最后，可能缺少一次跟新
            d_count = temp;
        }
        if(i_count >= d_count)
            return i_count;
        else return d_count;
    }
}