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…ch-1 Create MinimumNumberofRemovalstoMakeMountainArray.java
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/** | ||
1671. Minimum Number of Removals to Make Mountain Array | ||
Solved | ||
Hard | ||
Topics | ||
Companies | ||
Hint | ||
You may recall that an array arr is a mountain array if and only if: | ||
arr.length >= 3 | ||
There exists some index i (0-indexed) with 0 < i < arr.length - 1 such that: | ||
arr[0] < arr[1] < ... < arr[i - 1] < arr[i] | ||
arr[i] > arr[i + 1] > ... > arr[arr.length - 1] | ||
Given an integer array nums, return the minimum number of elements to remove to make nums a mountain array. | ||
**/ | ||
class Solution { | ||
public int minimumMountainRemovals(int[] nums) { | ||
int n = nums.length; | ||
int[] LIS = new int[n], LDS = new int[n]; | ||
Arrays.fill(LIS, 1); | ||
Arrays.fill(LDS, 1); | ||
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// Compute LIS for each index | ||
for (int i = 0; i < n; ++i) { | ||
for (int j = 0; j < i; ++j) { | ||
if (nums[i] > nums[j]) { | ||
LIS[i] = Math.max(LIS[i], LIS[j] + 1); | ||
} | ||
} | ||
} | ||
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// Compute LDS from each index | ||
for (int i = n - 1; i >= 0; --i) { | ||
for (int j = n - 1; j > i; --j) { | ||
if (nums[i] > nums[j]) { | ||
LDS[i] = Math.max(LDS[i], LDS[j] + 1); | ||
} | ||
} | ||
} | ||
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int maxMountainLength = 0; | ||
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// Find the maximum mountain length | ||
for (int i = 1; i < n - 1; ++i) { | ||
if (LIS[i] > 1 && LDS[i] > 1) { // Valid peak | ||
maxMountainLength = Math.max(maxMountainLength, LIS[i] + LDS[i] - 1); | ||
} | ||
} | ||
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return n - maxMountainLength; | ||
} | ||
} |