diff options
Diffstat (limited to 'datastructures/RMQ.cpp')
| -rw-r--r-- | datastructures/RMQ.cpp | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/datastructures/RMQ.cpp b/datastructures/RMQ.cpp new file mode 100644 index 0000000..b38b838 --- /dev/null +++ b/datastructures/RMQ.cpp @@ -0,0 +1,27 @@ +vector<int> values; +vector<vector<int>> rmq; + +int select(int a, int b) { + return values[a] <= values[b] ? a : b; +} + +void build() { + for(int i = 0, s = 1, ss = 1; s <= values.size(); ss=s, s*=2, i++) { + for(int l = 0; l + s <= values.size(); l++) { + if(i == 0) rmq[0][l] = l; + else { + int r = l + ss; + rmq[i][l] = select(rmq[i-1][l], rmq[i-1][r]]); +}}}} + +void init(vector<int>& v) { + values = v; + rmq = vector<vector<int>>(floor(log2(values.size()))+1, vector<int>(values.size())); + build(); +} + +int query(int l, int r) { + if(l >= r) return l; + int s = floor(log2(r-l)); r = r - (1 << s); + return select(rmq[s][l],rmq[s][r]); +}
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