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
67
68
69
70
71
72
73
74
75
76
77
|
#include <cmath>
#include <iostream>
#include <iterator>
#include <utility>
#include <vector>
using namespace std;
class SpiralIterator : public std::iterator<std::input_iterator_tag, int> {
struct SpiralInfinity { };
public:
pair<int, int> p;
int i, j, d;
SpiralIterator() : p{0,1}, i{2}, j{1}, d{-1}
{ }
auto begin() { return *this; }
auto end() { return SpiralInfinity{}; }
bool operator!=(SpiralInfinity) const { return true; } // infinite
auto operator*() { return p; }
auto operator++() {
switch (d) {
case 0: p.first--; break;
case 1: p.second--; break;
case 2: p.first++; break;
case 3: p.second++; break;
}
if (--j == 0) {
if (++d == 4) {
i += 2;
d = 0;
}
j = i;
if (d == 0) j--;
if (d == 3) j++;
}
}
};
int
manhattan(pair<int, int> c)
{
return abs(c.first) + abs(c.second);
}
int
main() {
int i;
cin >> i;
// part 1
SpiralIterator p1;
advance(p1, i-1);
cout << manhattan(*p1) << endl;
// part 2
const int N = 20;
vector<vector<int>> m(N, vector<int>(N, 0));
m[N/2][N/2] = 1;
for (auto [x,y] : SpiralIterator{}) {
x += N/2; y += N/2;
m[x][y] = m[x+1][y+1] + m[x+1][y] + m[x+1][y-1] +
m[ x ][y+1] + m[ x ][y-1] +
m[x-1][y+1] + m[x-1][y] + m[x-1][y-1];
if (m[x][y] > i) {
cout << m[x][y] << endl;
break;
}
}
}
|
