NOIP2015普及组 —— 推销员（salesman）

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#include <fstream>#include <algorithm>using namespace std;ifstream fin("salesman.in");ofstream fout("salesman.out");const int MAX_N = 100000, INT_MIN = 1<<31;struct Tnode{    int a, id;} a[MAX_N];int S[MAX_N], A[MAX_N], rmax[MAX_N];int Head_a = 0;bool cmp(const Tnode &, const Tnode &);void Build_a(int);void Build_rmax(int);int LMax();int RMax();void Update_a(int);void Update_rmax(int);int main(){    int N;    fin>>N;    for (int i=0; i<N; i++)        fin>>S[i];    for (int i=0; i<N; i++)        fin>>A[i];    Build_a(N);    Build_rmax(N);    int Last_Max = rmax[0];    int Ans = S[Last_Max]<<1+A[Last_Max];    fout<<Ans<<endl;    A[rmax[0]] = INT_MIN;    a[0].a = INT_MIN;    Update_rmax(rmax[0]);    int Left_Max_id, Right_Max_id, Left_Max, Right_Max;    for (int i=1; i<N; i++)    {        while (visit[a[Left_Max_id].id] && Left_Max_id<N)            Left_Max_id++;        Left_Max_id = LMax();        Right_Max_id = RMax();        Left_Max = A[Left_Max_id];        Right_Max = (S[Right_Max_id]-S[Last_Max_id])<<1 + A[Right_Max_id];        if (Left_Max > Right_Max)        {            Ans += Left_Max;            Last_Max = Left_Max_id;            Update_a(Left_Max_id);        }        else        {            Ans += Right_Max;            Last_Max = Right_Max_id;        //  Update_rmax(Right_Max_id);        }        fout<<Ans<<endl;    }    return 0;}bool cmp(const Tnode &A, const Tnode &B){    return A.a < B.a ? true : false;}void Build_a(int n){    for (int i=0; i<n; i++)        a[i].a = A[i];    sort(a, a+n, cmp);}void Build_rmax(int n){    rmax[n-1] = n-1;     int Right_Max = S[n-1]<<1 + A[n-1];    int Now_Max;    for (int i=n-2; i>=0; i--)    {        Now_Max = S[i]<<1 + A[i];        if (Now_Max > Right_Max)        {            rmax[i] = i;            Right_Max = Now_Max;        }        else            rmax[i] = rmax[i-1];    }}int LMax(){    return Head_a;}void Update_a(){    Head_a++;}
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