以下代码语法正确的是（ ）。
int m;cin >> m;switch (m) { case 1: cout << "item 1"; break; default: cout << "default item"; break; case 0: cout << "item 0"; break;}
int m;cin >> m;switch m:{ case 0: cout << "item 0"; break; case 1: cout << "item 1"; break; default: cout << "default item";}
int n = 1;int m;cin >> m;switch (m) { case 0: cout << "item 0"; break; case n: cout << "item 1"; break; default: cout << "default item";}
double m;cin >> m;switch (m) { default: cout << "default item"; break; case 0: cout << "item 0"; break; case 1: cout << "item 1"; break; }