LC 1687. Delivering Boxes from Storage to Ports (dp+slide window)

link

class Solution {
public:
    int boxDelivering(vector<vector<int>>& boxes, int portsCount, int maxBoxes, int maxWeight) {
        int n=boxes.size();
        vector<int> dp(n);
        int left=0;
        int right=1;
        int diff=1;
        int curW=boxes[0][1];
        dp[0]=2;
        while(right<n){
            if(boxes[right][0]!=boxes[right-1][0]) diff++;
            curW+=boxes[right][1];
            while(left<right && (right-left+1>maxBoxes || curW>maxWeight || (left>0 && dp[left]==dp[left-1]))){
                curW-=boxes[left][1];
                if(boxes[left][0]!=boxes[left+1][0]) diff--;
                left++;
            }
            dp[right]= left==0? diff+1 : dp[left-1]+diff+1;
            right++;
        }
        return dp[n-1];
    }
};

ref from zerotrac

class Solution {
public:
    int boxDelivering(vector<vector<int>>& boxes, int portsCount, int maxBoxes, int maxWeight) {
        int n=boxes.size();
        vector<int> diff(n);
        for(int i=1;i<n;i++){
            diff[i]=diff[i-1]+(boxes[i][0]!=boxes[i-1][0]);
        }
        vector<int> dp(n,INT_MAX);
        vector<int> f(n);
        deque<int> dq;
        vector<long long> wsum(n+1);
        for(int i=1;i<=n;i++) wsum[i]=wsum[i-1]+boxes[i-1][1];
        for(int i=0;i<n;i++){
            while(!dq.empty() && (i-dq.front()>maxBoxes || wsum[i+1]-wsum[dq.front()+1]>maxWeight)) dq.pop_front();
            if(i+1<=maxBoxes && wsum[i+1]<=maxWeight) dp[i]=diff[i]+2;
            
            if(!dq.empty()){
                dp[i]=min(dp[i],f[dq.front()]+diff[i]+2);
            }
            f[i]=dp[i]- (i<n-1? diff[i+1]:0);
            
            while(!dq.empty() && f[dq.back()]>=f[i]){
                dq.pop_back();
            }
            dq.push_back(i);
        }
        return dp[n-1];
    }
};