util/xorshift.cpp

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Last update: 2020-04-26 17:42:59+09:00

Required by

string/rolling_hash.cpp

Verified with

test/aoj0355.test.cpp

Code

#include <chrono>
class xor_shift {
    uint32_t x, y, z, w;
public:
    xor_shift() : x(static_cast<uint32_t>((chrono::system_clock::now().time_since_epoch().count())&((1LL << 32)-1))),
    y(1068246329), z(321908594), w(1234567890) {};

    uint32_t urand(){
        uint32_t t;
        t = x ^ (x << 11);
        x = y; y = z; z = w;
        w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
        return w;
    };

    int rand(int n){
        if(n < 0) return -rand(-n);
        uint32_t t = numeric_limits<uint32_t>::max()/(n+1)*(n+1);
        uint32_t e = urand();
        while(e >= t) e = urand();
        return static_cast<int>(e%(n+1));
    }

    int rand(int a, int b){
        if(a > b) swap(a, b);
        return a+rand(b-a);
    }
};

#line 1 "util/xorshift.cpp"
#include <chrono>
class xor_shift {
    uint32_t x, y, z, w;
public:
    xor_shift() : x(static_cast<uint32_t>((chrono::system_clock::now().time_since_epoch().count())&((1LL << 32)-1))),
    y(1068246329), z(321908594), w(1234567890) {};

    uint32_t urand(){
        uint32_t t;
        t = x ^ (x << 11);
        x = y; y = z; z = w;
        w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
        return w;
    };

    int rand(int n){
        if(n < 0) return -rand(-n);
        uint32_t t = numeric_limits<uint32_t>::max()/(n+1)*(n+1);
        uint32_t e = urand();
        while(e >= t) e = urand();
        return static_cast<int>(e%(n+1));
    }

    int rand(int a, int b){
        if(a > b) swap(a, b);
        return a+rand(b-a);
    }
};