update

src/8/18/sparsetable.cpp

@@ -0,0 +1,47 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <istream>
+#include <vector>
+
+using ll = int64_t;
+
+std::vector<ll> lg2,nums;
+std::vector<std::vector<ll>> st;
+
+int main(){
+    std::iostream::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+    ll n;
+    std::cin>>n;
+    ll q;
+    std::cin>>q;
+    nums.resize(n+1);
+    lg2.resize(1e5+5);
+    for(ll i=2;i<1e5+5;i++){
+        lg2[i]=lg2[i>>1]+1;
+    }
+    st.resize(n+1,std::vector<ll>(lg2[n]+2));
+    for(ll i=1;i<=n;i++){
+        std::cin>>nums[i];
+        st[i][0]=nums[i];
+    }
+    
+    for(ll j=1;j<lg2[n]+2;j++){
+        for(ll i=1;i<=n;i++){
+            if(i+(1ll<<j)-1>n){
+                break;
+            }
+            st[i][j]=std::max(st[i][j-1],st[i+(1ll<<(j-1))][j-1]);
+        }
+    }
+    while(q--){
+        ll l,r;
+        std::cin>>l>>r;
+        ll range = r-l+1;
+        ll k=lg2[range];
+        std::cout<<
+            std::max(st[l][k],st[r-(1ll<<k)+1][k])
+        <<"\n";
+    }
+}