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perf(P8818): 使用预计算的lg2数组优化对数计算

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用预计算的lg2数组替代多次log2调用，减少重复计算开销
This commit is contained in:
Zengtudor 2025-09-24 17:36:30 +08:00
parent cebbfa9891
commit 37ca18855a
1 changed files with 10 additions and 6 deletions
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16
src/9/23/P8818.cpp
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@ -23,9 +23,9 @@ do{\
printf(#v" :%lld\n",(v));\ printf(#v" :%lld\n",(v));\
}while(0)\ }while(0)\
const ll inf = 1e9+7; const ll inf = 1e9+7,maxn=1e5+5;
ll n,m,q; ll n,m,q;
std::vector<ll> a,b; std::vector<ll> a,b,lg2;
struct BT{ struct BT{
std::vector<std::vector<ll>> vmax, vmin, vupmin, vdownmax; std::vector<std::vector<ll>> vmax, vmin, vupmin, vdownmax;
@ -33,7 +33,7 @@ struct BT{
ll vsize; ll vsize;
inline BT(const std::vector<ll> &v){ inline BT(const std::vector<ll> &v){
vsize = ceil(log2(v.size())); vsize = ceil(lg2[v.size()]);
vmax.resize(v.size(),std::vector<ll>(vsize+1, -inf)); vmax.resize(v.size(),std::vector<ll>(vsize+1, -inf));
vmin.resize(v.size(),std::vector<ll>(vsize+1,inf)); vmin.resize(v.size(),std::vector<ll>(vsize+1,inf));
vupmin.resize(v.size(),std::vector<ll>(vsize+1,inf)); vupmin.resize(v.size(),std::vector<ll>(vsize+1,inf));
@ -63,14 +63,14 @@ struct BT{
// pv(vdownmax); // pv(vdownmax);
} }
inline ll getmax(const std::vector<std::vector<ll>> &v,const ll l,const ll r){ inline ll getmax(const std::vector<std::vector<ll>> &v,const ll l,const ll r){
const ll lg = log2(r-l+1); const ll lg = lg2[r-l+1];
return std::max( return std::max(
v[l][lg], v[l][lg],
v[r-(1ull<<lg)+1][lg] v[r-(1ull<<lg)+1][lg]
); );
} }
inline ll getmin(const std::vector<std::vector<ll>> &v,const ll l,const ll r){ inline ll getmin(const std::vector<std::vector<ll>> &v,const ll l,const ll r){
const ll lg = log2(r-l+1); const ll lg = lg2[r-l+1];
return std::min( return std::min(
v[l][lg], v[l][lg],
v[r-(1ull<<lg)+1][lg] v[r-(1ull<<lg)+1][lg]
@ -89,7 +89,7 @@ struct BT{
return getmin(vupmin, l, r); return getmin(vupmin, l, r);
} }
inline ll getis0(ll l,ll r){ inline ll getis0(ll l,ll r){
const ll lg = log2(r-l+1); const ll lg = lg2[r-l+1];
return vis0[l][lg] || vis0[r-(1ull<<lg)+1][lg]; return vis0[l][lg] || vis0[r-(1ull<<lg)+1][lg];
} }
}; };
@ -97,6 +97,10 @@ struct BT{
int main(){ int main(){
std::iostream::sync_with_stdio(false); std::iostream::sync_with_stdio(false);
std::cin.tie(nullptr); std::cin.tie(nullptr);
lg2.resize(maxn);
for(ll i=2;i<maxn;i++){
lg2[i]=lg2[i/2]+1;
}
std::cin>>n>>m>>q; std::cin>>n>>m>>q;
a.resize(n+1); a.resize(n+1);