63 lines
1.5 KiB
C++
63 lines
1.5 KiB
C++
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#include<bits/stdc++.h>
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using namespace std;
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const int MAX_N = 3e5+5;
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const int MAX_K = 19;
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int sMin[MAX_N][MAX_K];
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int sMax[MAX_N][MAX_K];
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int l2[MAX_N];
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#ifndef OITEST
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#define PRINT_VALUE(v)
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#endif
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int main(int argc,char* argv[]){
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#ifdef OITEST
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// #define PRINT_VALUE(v){cout<<#v<<" :"<<(v)<<endl;}
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// PRINT_VALUE(argv[0])
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string fileName="perfect";
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assert(argc==2);
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string num(argv[1]);
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string inputFileName = fileName+num+".in";
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string ansFileName = fileName+num+".ans";
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auto ansFile = ifstream(ansFileName);
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auto inputFile =ifstream(inputFileName);
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int correctAns;
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ansFile>>correctAns;
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#define cin inputFile
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#endif
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cin.sync_with_stdio(false);
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cin.tie(0);
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l2[0]=0;
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l2[1]=0;
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int n;
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cin>>n;
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for(int i=1;i<=n;i++){
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cin>>sMin[i][0];
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sMax[i][0]=sMin[i][0];
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}
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for(int i=2;i<=n;i++){
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l2[i]=l2[i/2]+1;
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}
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int k=l2[n]+1;
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for(int j=1;j<=k;j++){
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for(int i=1;i+(1<<j)-1<=n;i++){
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sMax[i][j]=max(sMax[i][j-1],sMax[i+(1<<(j-1))][j-1]);
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sMin[i][j]=min(sMin[i][j-1],sMin[i+(1<<(j-1))][j-1]);
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}
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}
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int ans=INT_MIN;
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for(int l=1;l<=n;l++){
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for(int r=l;r<=n;r++){
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int j=l2[r-l+1];
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int maxlr=max(sMax[l][j],sMax[r-(1<<j)+1][j]);
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int minlr=min(sMin[l][j],sMin[r-(1<<j)+1][j]);
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ans=max(ans,maxlr^minlr);
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}
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}
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cout<<ans<<endl;
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#ifdef OITEST
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assert(ans==correctAns);
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#endif
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}
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