hdu1754 I Hate It (线段树)

/*线段树 水题 模板套过*/
#include 
#include
#include
using namespace std;
#define max(a,b) a>b?a:b
struct LineTree
{
    int left,right;//左右区间端点
    int highest;//区间最大值
    LineTree *lchild,*rchild;
};

LineTree mem[400010];
int pos;
int score[200010];

LineTree *NewTree()    //自己做的时候内存一直超，这是网上学到的，还不是很明白
{
    LineTree *s=&mem[pos++];//如此分配空间
    return s;
}

LineTree* CreateTree(int a,int b)  //建立线段树
{
    LineTree *root=NewTree();
    root->left=a;
    root->right=b;
    if(b-a>1)
    {
        int mid;
        mid=(a+b)/2;
        root->lchild=CreateTree(a,mid);
        root->rchild=CreateTree(mid,b);
        root->highest=max(root->lchild->highest,root->rchild->highest);
    }
    else
        root->highest=max(score[root->left],score[root->right]);
    return root;
}

int search(LineTree *t,int a,int b)
{
    if(t->left==a && t->right==b)
        return t->highest;
    int mid=(t->left+t->right)/2;
    if(b<=mid)  return search(t->lchild,a,b);
    else if(mid<=a) return search(t->rchild,a,b);
    else
    {
        int s1,s2;
        s1=search(t->lchild,a,mid);
        s2=search(t->rchild,mid,b);
        return max(s1,s2);
    }
}

void update(LineTree *t,int a)
{
    if(t->right-t->left==1)
    {
        t->highest=max(score[t->left],score[t->right]);
        return;
    }
    if(t->lchild->right>=a)
        update(t->lchild,a);
    if(t->rchild->left<=a)
        update(t->rchild,a);
    t->highest=max(t->lchild->highest,t->rchild->highest);
    return;
}

int main()
{
    int n,m;
    LineTree *s;
    char ch;
    int a,b;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        pos=0;   //记得初始 - -！
        int i;
        for(i=1;i<=n;i++)
            scanf("%d",&score[i]);
        s=CreateTree(1,n);
        getchar();
        while(m--)
        {
            ch=getchar();
            scanf("%d%d",&a,&b);
            getchar();
            if(ch=='Q')
            {
                if(a==b) printf("%d\n",score[a]);
                else printf("%d\n",search(s,a,b));
            }
            else
            {
                score[a]=b;
                update(s,a);
            }
        }
    }
    return 0;
}