Leetcode-674 Longest Continuous Increasing

Longest Continuous Increasing

题目描述

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

Example

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. 

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

解法1

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，我们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。我们用一个变量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：

cpp

class Solution {
public:
    int findLengthOfLCIS(vector<int>& nums) {
        int res = 0, cnt = 0, pre = INT_MAX;
        for (int num : nums) {
            if (num > pre) ++cnt;
            else cnt = 1;
            res = max(res, cnt);
            pre = num;    
        }
        return res;
    }
};

Swift

class Solution {
    func findLengthOfLCIS(_ nums: [Int]) -> Int {
        var res = 0, cnt = 0, pre = Int.max
        for num in nums {
            if pre < num { cnt += 1 }
            else { cnt = 1 }
            res = max(res, cnt)
            pre = num
        }
        return res
    }
}

解法2

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：

class Solution {
public:
    int findLengthOfLCIS(vector<int> &nums) {
        int res = 0, cnt = 0, n = nums.size();
        for (int i = 0; i < n; i++) {
            if (i == 0 || nums[i - 1] < nums[i]) res = max(res, ++cnt);
            else cnt = 1
        }
        return res;
    }
}

Swift

class Solution {
    func findLengthOfLCIS(_ nums: [Int]) -> Int {
        var res = 0, cnt = 0, n = nums.count
        for i in 0..<n {
            if i == 0 || nums[i - 1] < nums[i] {
                cnt += 1
                res = max(res, cnt)
            } else {
                cnt = 1
            }
        }
        return res
    }
}

类似题目

Number of Longest Increasing Subsequence