leetcode(c++)(单调序列)

#include <iostream>
#include <vector>
#include <queue>
using namespace std;

vector<int>maxSlidingWindow(const vector<int>& nums,int k)
{
    int n = nums.size();
    deque<int>q;
    vector<int>res(n-k+1);
    for(int i = 0; i < n; ++i)
    {
        int start = i-k+1;
        while(!q.empty() && i - q.front() >= k)q.pop_front();
        while(!q.empty() && nums[q.front()] <= nums[i])q.pop_back();
        q.push_back(i);
        if(start >= 0)res[start] = nums[q.front()];
    }
    return res;
}

void print(const vector<int>& nums)
{
    for(auto num : nums)
    {
        cout << num << " ";
    }
    cout << endl;
}

int shortestSubarray(const vector<int>& A, int k)
{
    int n = A.size(),res = n + 1;
    vector<int>sum(n + 1);
    for(int i = 0; i < n; ++i)
    {
        sum[i+1] = sum[i] + A[i];
    }
    deque<int>q;
    for(int i = 0; i < n + 1 ; ++i)
    {
        while(!q.empty() && sum[i] - sum[q.front()] >= k)
        {
            res = min(res,i - q.front());
            q.pop_front();
        }
        while(!q.empty() && sum[q.front()] >= sum[i])q.pop_back();
        q.push_back(i);        
    }
    return res <= n ? res : -1;
}

int constrainedSubSum(const vector<int>& nums,int k)
{
    deque<int>q;
    int n = nums.size();
    vector<int>sum(n);
    int res = sum[0];
    for(int i = 0; i < n; ++i)
    {
        sum[i] = nums[i];
        if(!q.empty())sum[i]+=sum[q.front()];
        res = max(res,sum[i]);
        if(!q.empty() && i - q.front() >= k)q.pop_front();
        while(!q.empty() && sum[q.back()] <= sum[i])q.pop_back();
        if(sum[i] > 0)q.push_back(i);
    }
    return res;
}

int longestSubarry(const vector<int>& A,int limit)
{
    deque<int>maxd,mind;
    int left = 0, res = 0;
    for(int i = 0 ; i < A.size(); ++i)
    {
        while(!maxd.empty() && maxd.back() < A[i])maxd.pop_back();
        while(!mind.empty() && A[i] < mind.front())mind.pop_back();
        maxd.push_back(A[i]);
        mind.push_back(A[i]);
        if(maxd.front() - mind.front() > limit)
        {
            if(maxd.front() == A[left])maxd.pop_front();
            if(mind.front() == A[left])mind.pop_front();
            ++left;
        }
        res = max(res,i - left + 1);
    }    
    return res;
}

int maxResult(const vector<int>& nums,int k)
{
    int n = nums.size();
    vector<int>dp(n);
    dp[0] = nums[0];
    deque<int>q;
    q.push_back(0);
    for(int i = 0; i < n - 1;++i)
    {
        while(!q.empty() && i - q.front() >= k)q.pop_front();
        while(!q.empty() && dp[q.front()] <= dp[i])q.pop_back();
        q.push_back(i);
        dp[i+1]=dp[q.front()] + nums[i + 1]; 
    }
    return dp[n-1];
}

int main()
{
    //LeetCode239
    vector<int>nums{1,3,-1,-3,5,3,6,7};
    int k = 3;
    print(maxSlidingWindow(nums,k));

    //LeetCode862
    vector<int>A{1,2};
    k = 2;
    cout << shortestSubarray(A,k) << endl;

    //LeetCode1425
    nums = {10,2,-10,5,20};
    k = 2;
    cout << constrainedSubSum(nums,k) << endl;

    //LeetCode1438
    nums = {8,2,4,7};
    k = 4;
    cout << longestSubarry(nums,k) << endl;

    //LeetCode1696
    nums ={1,-1,-2,4,-7,3};
    k = 2;
    cout << maxResult(nums,k) << endl;
    return 0;
}