直接偏移100格就行，不用那么麻烦

#include<iostream>
int main () {
    std::ios::sync_with_stdio(false);
    char a[400][400];
    int n,m;
    char x;
    std::cin>>n>>m;
    for(int i = 1;i<=399;i++){
        for(int j = 1;j<=399;j++){
            a[i][j]=0;
        }
    }
    for(int i = 100;i<=n+99;i++){
        for(int j = 100;j<=m+99;j++){
            std::cin>>a[i][j];
        }
    }
    for(int i = 100;i<=n+99;i++){
        for(int j = 100;j<=m+99;j++){
            if(a[i][j]=='?')std::cout<<(a[i-1][j-1]=='*')+(a[i-1][j]=='*')+(a[i-1][j+1]=='*')+(a[i][j-1]=='*')+(a[i][j+1]=='*')+(a[i+1][j-1]=='*')+(a[i+1][j]=='*')+(a[i+1][j+1]=='*');else std::cout<<"*";
            
        }
    if(i!=n+99)std::cout<<"\n";
    }
}