365天挑战LeetCode1000题——Day 020 动态规划 18

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300. 最长递增子序列（116）

代码实现（思路看题解）

class Solution {
public:
    void binarySearch(vector<int>& d, const int num) {
        int l = 0;
        int r = d.size() - 1;
        int m;
        while (l < r) {
            m = l + r >> 1;
            if (d[m] >= num) r = m;
            else l = m + 1;
        }
        d[l] = num;
    }

    int lengthOfLIS(vector<int>& nums) {
        int n = nums.size();
        vector<int> d;
        d.push_back(nums[0]);
        for (int i = 1; i < n; i++) {
            if (nums[i] > d.back()) {
                d.push_back(nums[i]);
            }
            else binarySearch(d, nums[i]);
        }
        return d.size();
    }
};

376. 摆动序列（117）

代码实现（首刷自解）

class Solution {
public:
    int wiggleMaxLength(vector<int>& nums) {
        int n = nums.size();
        int pos = 1;
        int neg = 1;
        for (int i = 1; i < n; i++) {
            if (nums[i] > nums[i - 1]) {
                pos = max(pos, neg + 1);
                neg = neg;
            }
            else if (nums[i] < nums[i - 1]) {
                neg = max(neg, pos + 1);
                pos = pos;
            }
        }
        return max(pos, neg);
    }
};