默认生成一个uint_32。

        mt19937 rnd(time(0));
        uint mx = 0, mi = -1;
        printf("n=%d\n", n);
        for(int i = 1; i <= n; ++i) {
            uint res = rnd();
            cmax(mx, res);
            cmin(mi, res);
        }
        printf("mi=%u mx=%u\n", mi, mx);
//        n=200000000
//        mi=2 mx=4294967253

        mt19937_64 rnd(time(0));
        ull mx = 0, mi = -1;
        printf("n=%d\n", n);
        for(int i = 1; i <= n; ++i) {
            ull res = rnd();
            cmax(mx, res);
            cmin(mi, res);
        }
        printf("mi=%llu mx=%llu\n", mi, mx);
//        n=200000000
//        mi=48815069219 mx=18446744008811123758