线段树 - 3264 Balanced Lineup

大略的的看了线段树的定义然后就开始练手, 可能很多地方可以优化, 仅供参考.

徘徊在AC的边缘, 提交代码要把cout/cin 缓存 printf/scanf 刚好能过.

 #include <iostream>
 using namespace std;

 #define MAXN 50010

 struct Node{
     int left,right;
     int max,min;
     Node * pleft,*pright;
     Node():pleft(NULL),pright(NULL){}
     Node(int l,int r):left(l),right(r),max(-),min(0x7fffffff),pleft(NULL),pright(NULL){}
 };

 struct Point{
     int min;
     int max;
     Point(int ma,int mi):max(ma),min(mi){};
 };

 int heights[MAXN];

 void build(Node*p){
     if(p->left == p->right){
         p->max = heights[p->left];
         p->min = p->max;
         return;
     }
     //calc the max and min value.
     for (int i=p->left;i<=p->right;++i){
         if(heights[i]>p->max)
             p->max = heights[i];
         if(heights[i]<p->min)
             p->min = heights[i];
     }
     int mid = (p->left + p->right) >> ;
     p->pleft = new Node(p->left,mid);
     build(p->pleft);
     p->pright= new Node(mid+,p->right);
     build(p->pright);
 }

 Point query(Node * p, int left,int right){
     if(left==p->left && right == p->right)
         return Point(p->max,p->min);
     int mid = (p->left+p->right) >> ;
     if(left > mid)
         return query(p->pright,left,right);
     else if(right <= mid)
         return query(p->pleft,left,right);
     else{
         Point pl = query(p->pleft,left,mid);
         Point pr = query(p->pright,mid+,right);
         int tmin = pl.min < pr.min ? pl.min : pr.min;
         int tmax = pl.max > pr.max ? pl.max : pr.max;
         return Point(tmax,tmin);
     }
 }

 // for debug.
 void dfs(Node * p){
     if(p == NULL)
         return;
     cout<<"DFS TO: ["<<p->left<<", "<<p->right<<"] , ("<<p->max<<", "<<p->min<<")"<<endl;
     dfs(p->pleft);
     dfs(p->pright);
 }
 int main(){
     int N,Q;
     cin>>N>>Q;
     for(int i=;i<N;++i){
         cin>>heights[i];
     }
     Node * head = new Node(,N-);
     build(head);
     // dfs(head);

     int l,r;
     for(int i=;i<Q;++i){
         cin>>l>>r;
         Point point = query(head,l-,r-);
         cout<<point.max - point.min<<endl;
     }
     return ;
 }

AC代码:

#include <stdio.h>

#define MAXN 50010

struct Node{
    int left,right;
    int max,min;
    Node * pleft,*pright;
    Node():pleft(NULL),pright(NULL){}
    Node(int l,int r):left(l),right(r),max(-),min(0x7fffffff),pleft(NULL),pright(NULL){}
};

struct Point{
    int min;
    int max;
    Point(int ma,int mi):max(ma),min(mi){};
};

int heights[MAXN];

void build(Node*p){
    if(p->left == p->right){
        p->max = heights[p->left];
        p->min = p->max;
        return;
    }
    //calc the max and min value.
    for (int i=p->left;i<=p->right;++i){
        if(heights[i]>p->max)
            p->max = heights[i];
        if(heights[i]<p->min)
            p->min = heights[i];
    }
    int mid = (p->left + p->right) >> ;
    p->pleft = new Node(p->left,mid);
    build(p->pleft);
    p->pright= new Node(mid+,p->right);
    build(p->pright);
}

Point query(Node * p, int left,int right){
    if(left==p->left && right == p->right)
        return Point(p->max,p->min);
    int mid = (p->left+p->right) >> ;
    if(left > mid)
        return query(p->pright,left,right);
    else if(right <= mid)
        return query(p->pleft,left,right);
    else{
        Point pl = query(p->pleft,left,mid);
        Point pr = query(p->pright,mid+,right);
        int tmin = pl.min < pr.min ? pl.min : pr.min;
        int tmax = pl.max > pr.max ? pl.max : pr.max;
        return Point(tmax,tmin);
    }
}

// for debug.
// void dfs(Node * p){
//     if(p == NULL)
//         return;
//     cout<<"DFS TO: ["<<p->left<<", "<<p->right<<"] , ("<<p->max<<", "<<p->min<<")"<<endl;
//     dfs(p->pleft);
//     dfs(p->pright);
// }
int main(){
    int N,Q;
    scanf("%d%d",&N,&Q);
    for(int i=;i<N;++i){
        scanf("%d",&heights[i]);
    }
    Node * head = new Node(,N-);
    build(head);
    // dfs(head);

    int l,r;
    for(int i=;i<Q;++i){
        scanf("%d%d",&l,&r);
        Point point = query(head,l-,r-);
        printf("%d\n",point.max - point.min);
    }
    return ;
}