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Solution.cs
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45 lines (41 loc) · 1.33 KB
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public class Solution
{
public int[] MaxSlidingWindow(int[] nums, int k)
{
int n = nums.Length;
int[] segTree = new int[4 * n];
Build(segTree, nums, 0, n - 1, 1);
int len = n - k + 1;
int[] ret = new int[len];
for (int i = 0; i < len; i++)
{
ret[i] = Max(segTree, 0, n - 1, 1, i, i + k - 1);
}
return ret;
}
void Build(int[] segTree, int[] nums, int start, int end, int node)
{
if (start == end)
{
segTree[node] = nums[start];
return;
}
int mid = start + (end - start) / 2;
Build(segTree, nums, start, mid, 2 * node);
Build(segTree, nums, mid + 1, end, 2 * node + 1);
PushUp(segTree, node);
}
int Max(int[] segTree, int start, int end, int node, int qStart, int qEnd)
{
if (qStart > end || qEnd < start) return int.MinValue;
if (qStart <= start && qEnd >= end) return segTree[node];
int mid = start + (end - start) / 2;
int left = Max(segTree, start, mid, 2 * node, qStart, qEnd);
int right = Max(segTree, mid + 1, end, 2 * node + 1, qStart, qEnd);
return Math.Max(left, right);
}
void PushUp(int[] segTree, int node)
{
segTree[node] = Math.Max(segTree[2 * node], segTree[2 * node + 1]);
}
}