zoj 3031 / cdoj 430 - Robotruck - Southwestern Europe 2007

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O(n^2)代码：

#define CLEAR(a) memset((a),0,sizeof((a)))const int maxn=1e5+10;const int inf=1<<30;struct Point{    int x,y;    Point(){x=0;y=0;};    Point(int x,int y){this->x=x;this->y=y;};} point[maxn];int w[maxn];typedef pair<int,int> pr;int disp(Point p1,Point p2){    return abs(p1.x-p2.x)+abs(p1.y-p2.y);}int f[maxn];int main(){    int T,kase=0;    scanf("%d",&T);    while(T--)    {        CLEAR(f);CLEAR(w);        int n,c;        scanf("%d%d",&c,&n);        for(int i=1;i<=n;i++)        {            int x,y;            scanf("%d%d%d",&x,&y,&w[i]);            point[i]=Point(x,y);        }        f[0]=0;        //f[1]=2*disp(point[0],point[1]);        for(int i=1;i<=n;++i)//若为i++，应如何修改？        {            int sw=w[i],d=disp(point[0],point[i]);            f[i]=inf;            for(int j=i-1;sw<=c&&j>=0;--j)//若为j--，应如何修改？            {                f[i]=min(f[i],f[j]+d+disp(point[0],point[j+1]));                sw+=w[j];d+=disp(point[j],point[j+1]);            }            //cout<<f[i]<<endl;        }        printf("Case %d: %d\n",++kase,f[n]);    }    return 0;}

单调队列优化，状态转移方程做了一些调整

#define CLEAR(a) memset((a),0,sizeof((a)))typedef long long LL;const int maxn=1e5+10;const int inf=1<<30;struct Point{    int x,y;    Point(){x=0;y=0;};    Point(int x,int y){this->x=x;this->y=y;};} point[maxn];struct pr{    LL first,second;    pr(){};    pr(int a,int b):first(a),second(b){};    bool operator< (const pr &a) const    {        if (second==a.second) return first>a.first;        else return second>a.second;    }};LL disp(Point p1,Point p2){    return abs(p1.x-p2.x)+abs(p1.y-p2.y);}LL f[maxn],s[maxn],sw[maxn],w[maxn];template <class T>class Priority_Queue{private:    T qnode[maxn];    int head,rear;public:    Priority_Queue()    {        head=rear=0;    };    bool empty()    {        return head==rear;    }    T top()    {        return qnode[head];    };    void pop()    {        if (head<rear) head++;    }    void pop(int id,int c)    {        while ( head < rear && sw[id] - sw[qnode[head].first-1]  > c ) head++;    }    void push(T node)    {        while (rear > head && qnode[rear - 1].second > node.second)        {            rear--;        }        qnode[rear++]=node;    }};int main(){    int T,kase=0;    scanf("%d",&T);    while(T--)    {        CLEAR(f);CLEAR(s);CLEAR(sw);        int n,c;        scanf("%d%d",&c,&n);        bool reach=1;        for(int i=1;i<=n;i++)        {            int x,y;            scanf("%d%d%lld",&x,&y,&w[i]);            if (w[i]>c) reach=0;            point[i]=Point(x,y);            sw[i]=sw[i-1]+w[i];            s[i]=s[i-1]+disp(point[i-1],point[i]);        }        f[0]=0;        Priority_Queue<pr> q;        //q.push(pr(0,0));        for(int i=1;i<=n;++i)        {            LL d=disp(point[0],point[i]);            q.push(pr(i,f[i-1]-s[i]+d));            q.pop(i,c);            pr k=q.top();            f[i]=k.second+s[i]+d;            //cout<<f[i]<<endl;        }        if (reach) printf("%lld\n",f[n]);        else printf("0\n");    }    return 0;}

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