pat (a1013 & a1024)

连着两道大数模拟题,没啥技巧,老老实实写个BigNumber(python和java选手请无视)。

坑点是注意重载默认构造函数,否则此类直接访问未初始化数组的Undefined Behavior会让你莫名其妙Wrong Answer到死。

A1023. Have Fun with Numbers

代码

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
using namespace std;
struct {
int digits[25];
int sorted[25];
int len;
BigNumber() {
memset(digits, 0, sizeof(digits));
memset(sorted, 0, sizeof(sorted));
len = 0;
}
void Read() {
char s[25];
scanf("%s", s);
len = strlen(s);
for (int i = 0; i < len; ++i) {
digits[i] = s[len - 1 - i] - '0';
}
}
void SortDigits() {
for (int i = 0; i < len; ++i) {
sorted[i] = digits[i];
}
sort(sorted, sorted + len);
}
BigNumber Doubled() {
BigNumber n;
n.len = len;
for (int i = 0; i < n.len; ++i) {
n.digits[i + 1] = (n.digits[i] + digits[i] * 2) / 10;
n.digits[i] = (n.digits[i] + digits[i] * 2) % 10;
}
if (n.digits[len] > 0) {
++n.len;
}
return n;
}
void Print() {
for (int i = len - 1; i >= 0; --i) {
printf("%d", digits[i]);
}
puts("");
}
bool IsSamePermutation(BigNumber other) {
if (len != other.len) {
return false;
}
SortDigits();
other.SortDigits();
for (int i = 0; i < len; ++i) {
if (sorted[i] != other.sorted[i]) {
return false;
}
}
return true;
}
};
int main() {
BigNumber n;
n.Read();
BigNumber m = n.Doubled();
puts(n.IsSamePermutation(m) ? "Yes" : "No");
m.Print();
return 0;
}

A1024. Palindromic Number

代码

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
using namespace std;
struct {
int digits[100];
int len;
BigNumber() {
memset(digits, 0, sizeof(digits));
len = 0;
}
BigNumber operator + (const BigNumber &other) const {
BigNumber sum;
sum.len = max(len, other.len);
for (int i = 0; i < sum.len; ++i) {
sum.digits[i + 1] = (sum.digits[i] + digits[i] + other.digits[i]) / 10;
sum.digits[i] = (sum.digits[i] + digits[i] + other.digits[i]) % 10;
}
if (sum.digits[sum.len] > 0) {
++sum.len;
}
return sum;
}
BigNumber Reverse() {
BigNumber r = *this;
reverse(r.digits, r.digits + r.len);
for (; r.len > 0 && r.digits[r.len - 1] == 0; --r.len);
return r;
}
bool IsPalindromic() {
for (int i = 0; i < len / 2; ++i) {
if (digits[i] != digits[len - 1 - i]) {
return false;
}
}
return true;
}
void Read() {
char s[20];
scanf("%s", s);
len = strlen(s);
for (int i = 0; i < len; ++i) {
digits[i] = s[len - 1 - i] - '0';
}
}
void Print() {
for (int i = len - 1; i >= 0; --i) {
printf("%d", digits[i]);
}
puts("");
}
};
int main() {
BigNumber n;
int k;
n.Read();
scanf("%d", &k);
int i;
for (i = 0; i < k; ++i) {
if (n.IsPalindromic()) {
break;
}
n = n + n.Reverse();
}
n.Print();
printf("%dn", i);
return 0;
}