非常简单

#include <bits/stdc++.h>
using namespace std;
const int N = 1e9;
#define ll long long
int main(){
    string a;
    getline(cin,a);
    ll len = a.size();
    for(int i=0;i<len;i++){
        if(a[i] != ' ') cout << a[i];
        else if(a[i] == ' ') cout << "*";
    }
    return 0;
}