feat: fastset

Author: ttamx

data-structure/fast-set.hpp

@@ -0,0 +1,92 @@
+#pragma once
+#include "template.hpp"
+
+/**
+ * Author: Teetat T.
+ * Date: 2026-04-16
+ * Description: Fast Set
+ */
+
+struct FastSet{
+    using u64 = uint64_t;
+
+    int n,len;
+    vector<u64> t;
+
+    FastSet(){}
+    FastSet(int n){build(n);}
+
+    int size(){return n;}
+    void build(int _n){
+        assert(_n>=0);
+        n=_n;
+        len=1;
+        while((len<<6)<n)len<<=6;
+        len/=63;
+        t.resize(len+(n+63)/64);
+    }
+
+    bool count(int i)const{
+        assert(0<=i&&i<n);
+        return t[len+(i>>6)]>>(i&63)&1;
+    }
+    void insert(int x){
+        assert(0<=x&&x<n);
+        int i=len+(x>>6),j=x&63;
+        while(true){
+            if(t[i]>>j&1ULL)return;
+            t[i]|=1ULL<<j;
+            if(!i)return;
+            j=(--i)&63;
+            i>>=6;
+        }
+    }
+    void erase(int x){
+        assert(0<=x&&x<n);
+        int i=len+(x>>6),j=x&63;
+        while(true){
+            t[i]&=~(1ULL<<j);
+            if(!i||t[i])return;
+            j=(--i)&63;
+            i>>=6;
+        }
+    }
+    int next(int x){
+        if(x>=n)return n;
+        if(x<0)x=0;
+        if(count(x))return x;
+        int i=len+(x>>6),j=x&63;
+        while(true){
+            if(t[i]&((~1ULL)<<j)){
+                j=__builtin_ctzll(t[i]&((~1ULL)<<j));
+                if(i>=len)return (i-len)*64+j;
+                break;
+            }
+            if(!i)return n;
+            j=(--i)&63;
+            i>>=6;
+        }
+        i=i*64+j+1;
+        while(i<len)i=i*64+__builtin_ctzll(t[i])+1;
+        return (i-len)*64+__builtin_ctzll(t[i]);
+    }
+    int prev(int x){
+        if(x<0)return -1;
+        if(x>=n)x=n-1;
+        if(count(x))return x;
+        int i=len+(x>>6),j=x&63;
+        while(true){
+            if(t[i]&((1ULL<<j)-1ULL)){
+                j=63-__builtin_clzll(t[i]&((1ULL<<j)-1ULL));
+                if(i>=len)return (i-len)*64+j;
+                break;
+            }
+            if(!i)return -1;
+            j=(--i)&63;
+            i>>=6;
+        }
+        i=i*64+j+1;
+        while(i<len)i=i*64+64-__builtin_clzll(t[i]);
+        return (i-len)*64+63-__builtin_clzll(t[i]);
+    }
+};

verify/yosupo/data-structure/predecessor_problem.test.cpp

@@ -0,0 +1,30 @@
+#define PROBLEM "https://judge.yosupo.jp/problem/predecessor_problem"
+#include "template.hpp"
+#include "data-structure/fast-set.hpp"
+
+int main(){
+    cin.tie(nullptr)->sync_with_stdio(false);
+    int n,q;
+    cin >> n >> q;
+    string t;
+    cin >> t;
+    FastSet fs(n);
+    for(int i=0;i<n;i++)if(t[i]=='1')fs.insert(i);
+    while(q--){
+        int op,k;
+        cin >> op >> k;
+        if(op==0){
+            fs.insert(k);
+        }else if(op==1){
+            fs.erase(k);
+        }else if(op==2){
+            cout << fs.count(k) << "\n";
+        }else if(op==3){
+            int x=fs.next(k);
+            if(x==n)x=-1;
+            cout << x << "\n";
+        }else{
+            cout << fs.prev(k) << "\n";
+        }
+    }
+}