33 lines
1.4 KiB
C++
33 lines
1.4 KiB
C++
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template<typename _Tp, typename _Op = function<_Tp(const _Tp&, const _Tp&)>> struct sparse_table_2d {
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_Op op;
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vector<vector<vector<vector<_Tp>>>> st;
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sparse_table_2d(const vector<vector<_Tp>>& a, _Op&& __operation) {
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op = __operation;
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int n = a.size();
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int m = int(log2(n) + 1);
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st = vector(n, vector(n, vector(m, vector<_Tp>(m))));
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for (int k = 0; k < m; ++k) {
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for (int l = 0; l < m; ++l) {
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for (int i = 0; i + (1 << k) <= n; ++i) {
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for (int j = 0; j + (1 << l) <= n; ++j) {
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if (k == 0) {
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if (l == 0) {
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st[i][j][k][l] = a[i][j];
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} else {
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st[i][j][k][l] = op(st[i][j][k][l - 1], st[i][j + (1 << l - 1)][k][l - 1]);
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}
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} else {
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st[i][j][k][l] = op(st[i][j][k - 1][l], st[i + (1 << k - 1)][j][k - 1][l]);
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}
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}
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}
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}
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}
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}
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_Tp query(size_t x1, size_t y1, size_t x2, size_t y2) {
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int s1 = lg2(x2 - x1 + 1);
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int s2 = lg2(y2 - y1 + 1);
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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])));
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}
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};
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