hdu 1754 I Hate It

http://acm.hdu.edu.cn/showproblem.php?pid=1754

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <algorithm>

  4 #define maxn 300000

  5 using namespace std;

  6 

  7 int a[maxn];

  8 int max2;

  9 struct node

 10 {

 11     int l,r,max1;

 12 }tree[maxn*4];

 13 

 14 

 15 void build(int i,int l,int r)

 16 {

 17     tree[i].l=l;

 18     tree[i].r=r;

 19     if(l==r)

 20     {

 21         tree[i].max1=a[l];

 22         return;

 23     }

 24     int mid=(l+r)>>1;

 25     build(i<<1,l,mid);

 26     build(i<<1|1,mid+1,r);

 27     tree[i].max1=max(tree[i<<1].max1,tree[i<<1|1].max1);

 28 }

 29 

 30 void update(int i,int idx,int key)

 31 {

 32     if(tree[i].l==tree[i].r)

 33     {

 34         tree[i].max1=key;

 35         return ;

 36     }

 37     int mid=(tree[i].l+tree[i].r)>>1;

 38     if(idx<=mid)

 39     {

 40          update(i<<1,idx,key);

 41     }

 42     else

 43         update(i<<1|1,idx,key);

 44     tree[i].max1=max(tree[i<<1].max1,tree[i<<1|1].max1);

 45 }

 46 

 47 void search1(int i,int l,int r)

 48 {

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

 50     {

 51         max2=max(max2,tree[i].max1);

 52         return ;

 53     }

 54     int mid=(tree[i].l+tree[i].r)>>1;

 55     if(r<=mid)

 56     {

 57         search1(i<<1,l,r);

 58     }

 59     else if(l>mid)

 60     {

 61         search1(i<<1|1,l,r);

 62     }

 63     else

 64     {

 65         search1(i<<1,l,mid);

 66         search1(i<<1|1,mid+1,r);

 67     }

 68 }

 69 

 70 

 71 int main()

 72 {

 73     int N,M;

 74     while(scanf("%d%d",&N,&M)!=EOF)

 75     {

 76         for(int i=1; i<=N; i++)

 77         {

 78             scanf("%d",&a[i]);

 79         }

 80         getchar();

 81         build(1,1,N);

 82         for(int i=1; i<=M; i++)

 83         {

 84             char ch;

 85             int a,b;

 86             scanf("%c %d%d",&ch,&a,&b);

 87             getchar();

 88             if(ch=='Q')

 89             {

 90                 max2=-1;

 91                 search1(1,a,b);

 92                 printf("%d\n",max2);

 93             }

 94             else if(ch=='U')

 95             {

 96                 update(1,a,b);

 97             }

 98         }

 99     }

100     return 0;

101 }

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