HDU 1754 I Hate It【线段树 单点更新】

题意：给出n个数，每次操作修改它的第s个数，询问给定区间的数的最大值

把前面两道题结合起来就可以了

 

自己还是敲不出来-------------

  1 #include<iostream>  

  2 #include<cstdio>  

  3 #include<cstring> 

  4 #include <cmath> 

  5 #include<stack>

  6 #include<vector>

  7 #include<map> 

  8 #include<set>

  9 #include<queue> 

 10 #include<algorithm>  

 11 using namespace std;

 12 

 13 typedef long long LL;

 14 const int INF = (1<<30)-1;

 15 const int mod=1000000007;

 16 const int maxn=200005;

 17 

 18 int n,m;

 19 int a[maxn];

 20 int nmax;

 21 

 22 struct node{

 23     int l,r;

 24     int nmax;

 25 } tree[4*maxn];

 26 

 27 char s[105];

 28 

 29 

 30 void build_tree(int i,int l,int r){

 31     tree[i].l=l;

 32     tree[i].r=r;

 33     if(l==r){

 34         tree[i].nmax=a[l];

 35         return;

 36     }

 37     int mid=(l+r)/2;

 38     build_tree(2*i,l,mid);

 39     build_tree(2*i+1,mid+1,r);

 40     tree[i].nmax=max(tree[2*i].nmax,tree[2*i+1].nmax);

 41 }

 42 

 43 void update(int i,int s,int w){

 44     if(tree[i].l==tree[i].r){

 45         tree[i].nmax=w;

 46         return;

 47     }

 48     

 49       int mid=(tree[i].l + tree[i].r)/2;

 50       if(s<=mid) update(2*i,s,w);

 51       else update(2*i+1,s,w);

 52       

 53      tree[i].nmax=max(tree[2*i].nmax,tree[2*i+1].nmax);

 54 }

 55 

 56 void query(int i,int l,int r){//查询 

 57      if(tree[i].nmax<=nmax) return;

 58      if(tree[i].l==l&&tree[i].r==r){

 59          nmax = max(tree[i].nmax,nmax);

 60          return;

 61      }

 62      int mid=(tree[i].l+tree[i].r)/2;

 63      if(r<=mid) query(2*i,l,r);

 64      else if(l>mid) query(2*i+1,l,r);

 65      else{

 66          query(2*i,l,mid);

 67          query(2*i+1,mid+1,r);

 68      }

 69  }

 70 

 71 

 72 int main(){

 73     while(scanf("%d %d",&n,&m)!=EOF){

 74         memset(tree,0,sizeof(tree));

 75         for(int i=1;i<=n;i++) scanf("%d",&a[i]);

 76         

 77         build_tree(1,1,n);

 78         

 79         while(m--){

 80             scanf("%s",s);

 81             if(s[0]=='Q'){

 82                 int l,r;

 83                 scanf("%d %d",&l,&r);

 84                 

 85                 nmax=-INF;

 86                 query(1,l,r);

 87                 

 88                 printf("%d\n",nmax);                

 89             }

 90             if(s[0]=='U'){

 91                 int u,v;

 92                 scanf("%d %d",&u,&v);

 93                 update(1,u,v);            

 94             }

 95             

 96         }            

 97     

 98     }

 99     return 0;    

100 }

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加油啊---gooooooooooooooooooooooo