• 正无穷

memset(a,127,sizeof(a));

• 负无穷

memset(a,128,sizeof(a));

• 正无穷的一半

memset(a,60,sizeof(a));
memset(a,0x3f,sizeof(a));

• 赋值0

memset(a,0,sizeof(a));

• 赋值-1

memset(a,-1,sizeof(a));

• 二维数组

#include <bits/stdc++.h>

using namespace std;
const int N = 10;
int a[N][N];

int main() {
    int cnt = 0;
    for (int i = 0; i < N; i++)
        for (int j = 0; j < N; j++)
            a[i][j] = ++cnt;

    memset(a, 0, sizeof(a));
    
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++)
            cout << a[i][j] << ' ';
        cout << endl;
    }

    return 0;
}