hdu-1754 I Hate It 线段树

来源：互联网发布：图像语义分割知乎编辑：程序博客网时间：2024/04/29 04:53
http://acm.hdu.edu.cn/showproblem.php?pid=1754
求区间最大数，并且有单点操作
#include <iostream>#include <cstdio>#include <cmath>#include <cstring>#include <string>#include <algorithm>using namespace std;#define MAX 200010typedef struct{    int l;    int r;    int max;} Tree;Tree tree[MAX*4];int build(int i,int l,int r)  //建树{    int mid;    tree[i].l=l;    tree[i].r=r;    tree[i].max=0;    if(l==r)    {        return 0;    }    mid=(l+r)/2;    build(i*2,l,mid);    build(i*2+1,mid+1,r);}int insert(int i,int k,int v)  //插入{    tree[i].max=v >tree[i].max?v:tree[i].max;    if(tree[i].l==tree[i].r)       return 0;    else    {        int mid=(tree[i].l+tree[i].r)/2;        if(mid<k)            insert(i*2+1,k,v);        else            insert(i*2,k,v);    }}int del(int i,int k,int v)  //先删除{   if(tree[i].l==tree[i].r)   {       tree[i].max=v;       return i;   }   else   {       int mid=(tree[i].l+tree[i].r)/2;       if(mid<k)          del(i*2+1,k,v);        else          del(i*2,k,v);   }}void change(int i)  //再倒着更新{    if(i==1)        return ;    if(i%2==1)    {        tree[(i-1)/2].max=max(tree[i-1].max,tree[i].max);        change((i-1)/2);    }    else    {        tree[i/2].max=max(tree[i].max,tree[i+1].max);        change(i/2);    }}int findmax(int i,int x,int y)  //找区间的最大{    int ans=0,mid;    if((x<=tree[i].l)&&(y>=tree[i].r))        return tree[i].max;    ans=0;    mid=(tree[i].l+tree[i].r)/2;    if (x<=mid)  ans= max(ans,findmax(i*2,x,y));    if (y>mid)   ans= max(ans,findmax(i*2+1,x,y));    return ans;}int N,M;int main(){    while(~scanf("%d%d",&N,&M))    {        build(1,1,N);        int a;        char Q[3];        for(int i=1; i<=N; i++)        {            scanf("%d",&a);            insert(1,i,a);        }        for(int i=1; i<=M; i++)        {            scanf("%s",Q);            if(Q[0]=='Q')            {                int x,y;                scanf("%d%d",&x,&y);                printf("%d\n",findmax(1,x,y));            }            else            {                int i,v;                scanf("%d%d",&i,&v);                int t=del(1,i,v);                change(t);            }        }    }}