BZOJ 3747 POI 2015 Kinoman line segment tree

BZOJ 3747 POI 2015 Kinoman line segment tree

The sequence of showing a movie in a cinema. A movie gets its weight only once it is viewed. You cannot obtain the weight value if you haven't read it or read it twice or more. Q: What is the maximum weight that can be obtained by watching movies in a continuous interval.

Idea: Use the line segment tree to maintain the prefix and. Add the weight of the first place to the weight of the movie, and then subtract the weight of the movie from the weight of the second place. Start of enumeration. Update the answer first, subtract twice the weight value from the current node, and then add the weight value next time (I don't think I understand, let's take a look at the code...

CODE:

#include 
 
  #include 
  
   #include 
   
    #include #define MAX 1000010using namespace std;#define LEFT (pos << 1)#define RIGHT (pos << 1|1) struct SegTree{    long long _max,c;}tree[MAX << 2]; int total,cnt;int src[MAX],value[MAX];int first[MAX],last[MAX],next[MAX]; inline void PushDown(int pos){    if(tree[pos].c) {        tree[LEFT]._max += tree[pos].c;        tree[RIGHT]._max += tree[pos].c;        tree[LEFT].c += tree[pos].c;        tree[RIGHT].c += tree[pos].c;        tree[pos].c = 0;    }} inline void Modify(int l,int r,int x,int y,int c,int pos){    if(l == x && y == r) {        tree[pos]._max += c;        tree[pos].c += c;        return ;    }    PushDown(pos);    int mid = (l + r) >> 1;    if(y <= mid) Modify(l,mid,x,y,c,LEFT);    else if(x > mid) Modify(mid + 1,r,x,y,c,RIGHT);    else {        Modify(l,mid,x,mid,c,LEFT);        Modify(mid + 1,r,mid + 1,y,c,RIGHT);    }    tree[pos]._max = max(tree[LEFT]._max,tree[RIGHT]._max);} inline long long Ask(int l,int r,int x,int y,int pos){    if(l == x && y == r)        return tree[pos]._max;    PushDown(pos);    int mid = (l + r) >> 1;    if(y <= mid) return Ask(l,mid,x,y,LEFT);    if(x > mid)      return Ask(mid + 1,r,x,y,RIGHT);    long long left = Ask(l,mid,x,mid,LEFT);    long long right = Ask(mid + 1,r,mid + 1,y,RIGHT);    return max(left,right);} int main(){    cin >> total >> cnt;    for(int i = 0; i < MAX; ++i) next[i] = total + 1;    for(int i = 1; i <= total; ++i) {        scanf("%d",&src[i]);        if(!first[src[i]]) {            first[src[i]] = i;            last[src[i]] = i;        }        else {            next[last[src[i]]] = i;            last[src[i]] = i;        }    }    for(int i = 1; i <= cnt; ++i)        scanf("%d",&value[i]);    for(int i = 1; i <= cnt; ++i)        if(first[i]) {            Modify(1,total + 1,first[i],total + 1,value[i],1);            Modify(1,total + 1,next[first[i]],total + 1,-value[i],1);        }    long long ans = 0;    for(int i = 1; i <= total; ++i) {        ans = max(ans,Ask(1,total,i,total,1));        Modify(1,total + 1,i,total + 1,-value[src[i]],1);        Modify(1,total + 1,next[i],total + 1,value[src[i]] << 1,1);        Modify(1,total + 1,next[next[i]],total + 1,-value[src[i]],1);    }    cout << ans << endl;    return 0;}