memset

可初始化0，-1 （可初始化数组 或 结构体等）（因为是对每个字节操作，char 只有一个字节 所以初始化很方便）

初始化最大值 inf：memset(a,0x3f,sizeof(a)) （即把每个字节变为0x3f 所以int 或 long long都是这个写法）

#include <bits/stdc++.h>
#define mst(a,val) memset(a,val,sizeof(a))
#define ll long long
using namespace std;
const int inf = 0x3f3f3f3f; //9
const ll inff = 0x3f3f3f3f3f3f3f3f; //18

int a[10];
ll b[10];
struct Node
{
    int a;
    ll b;
}c[10];

int main()
{
    mst(a,0x3f);
    cout<<hex<<a[0]<<"   "<<dec<<a[0]<<"   "<<inf<<endl<<endl;

    mst(b,0x3f);
    cout<<hex<<b[0]<<"   "<<dec<<b[0]<<"   "<<inff<<endl<<endl;

    mst(c,0x3f);
    cout<<hex<<c[0].a<<"   "<<dec<<c[0].a<<"   "<<inf<<endl;
    cout<<hex<<c[0].b<<"   "<<dec<<c[0].b<<"   "<<inff<<endl<<endl;

    mst(c,0);
    cout<<hex<<c[0].a<<"   "<<dec<<c[0].a<<endl;
    cout<<hex<<c[0].b<<"   "<<dec<<c[0].b<<endl<<endl;
}