46 lines
1.0 KiB
C++
46 lines
1.0 KiB
C++
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#include<bits/stdc++.h>
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using namespace std;
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#define PRINT_VALUE(v){cout<<#v<<" :"<<v<<endl;}
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struct SparseTable{
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private:
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vector<vector<int>> st;
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vector<int> log;
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int n;
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public:
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SparseTable(const vector<int> &arr){
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n=arr.size();
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int K=log2(n)+1;
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st.assign(n,vector<int>(K));
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log.assign(n+1,0);
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log[1]=0;
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for(int i=2;i<=n;i++){
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log[i]=log[i/2]+1;
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}
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for(int i=0;i<n;i++){
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st[i][0]=arr[i];
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}
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for(int j=1;j<=K;j++){
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for(int i=0;(i+(1<<j))<=n;i++){
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st[i][j]=min(st[i][j-1],st[i+(1<<(j-1))][j-1]);
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}
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}
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}
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int query(int l,int r){
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int j=this->log[r-l+1];
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return min(this->st[l][j],this->st[r-(1<<j)+1][j]);
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//因为log[i]向下取整，所以此时r>=(1<<j)求右边的区间就是st[]
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}
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};
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int main(){
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vector<int> v={1, 3, 5, 7, 9, 11};
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SparseTable st_min(v);
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// PRINT_VALUE(st_min.query(1,2));
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PRINT_VALUE(st_min.query(1, 4));
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}
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