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Add trees/sparse_table_2d.cc 

Signed-off-by: subcrip <contact@subc.rip>
This commit is contained in:
subcrip 2024-09-08 14:49:18 +08:00
parent 26b73ce439
commit f666edf536
1 changed files with 32 additions and 0 deletions
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trees/sparse_table_2d.cc Normal file
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template<typename _Tp, typename _Op = function<_Tp(const _Tp&, const _Tp&)>> struct sparse_table_2d {
_Op op;
vector<vector<vector<vector<_Tp>>>> st;
sparse_table_2d(const vector<vector<_Tp>>& a, _Op&& __operation) {
op = __operation;
int n = a.size();
int m = int(log2(n) + 1);
st = vector(n, vector(n, vector(m, vector<_Tp>(m))));
for (int k = 0; k < m; ++k) {
for (int l = 0; l < m; ++l) {
for (int i = 0; i + (1 << k) <= n; ++i) {
for (int j = 0; j + (1 << l) <= n; ++j) {
if (k == 0) {
if (l == 0) {
st[i][j][k][l] = a[i][j];
} else {
st[i][j][k][l] = op(st[i][j][k][l - 1], st[i][j + (1 << l - 1)][k][l - 1]);
}
} else {
st[i][j][k][l] = op(st[i][j][k - 1][l], st[i + (1 << k - 1)][j][k - 1][l]);
}
}
}
}
}
}
_Tp query(size_t x1, size_t y1, size_t x2, size_t y2) {
int s1 = lg2(x2 - x1 + 1);
int s2 = lg2(y2 - y1 + 1);
return op(st[x1][y1][s1][s2], op(st[x2 - (1 << s1) + 1][y1][s1][s2], op(st[x1][y2 - (1 << s2) + 1][s1][s2], st[x2 - (1 << s1) + 1][y2 - (1 << s2) + 1][s1][s2])));
}
};