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longest-strictly-increasing-or-strictly-decreasing-subarray.cpp
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longest-strictly-increasing-or-strictly-decreasing-subarray.cpp
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// Time: O(n)
// Space: O(1)
// array
class Solution {
public:
int longestMonotonicSubarray(vector<int>& nums) {
const auto& cmp = [](int x, int y) {
return x < y ? -1 : (x > y ? 1 : 0);
};
int result = 1;
for (int i = 1, cnt = 1, curr = 0, prev = 0; i < size(nums); ++i, prev = curr) {
curr = cmp(nums[i - 1], nums[i]);
if (curr == 0) {
cnt = 1;
continue;
}
cnt = (curr == prev ? cnt : 1) + 1;
result = max(result, cnt);
}
return result;
}
};
// Time: O(n)
// Space: O(1)
// array
class Solution2 {
public:
int longestMonotonicSubarray(vector<int>& nums) {
int result = 1;
for (int i = 1, cnt1 = 1, cnt2 = 1; i < size(nums); ++i) {
if (nums[i - 1] < nums[i]) {
++cnt1;
cnt2 = 1;
} else if (nums[i - 1] > nums[i]) {
++cnt2;
cnt1 = 1;
} else {
cnt1 = cnt2 = 1;
}
result = max({result, cnt1, cnt2});
}
return result;
}
};
// Time: O(n)
// Space: O(1)
// array
class Solution3 {
public:
int longestMonotonicSubarray(vector<int>& nums) {
const auto& f = [&](const auto& compare) {
int result = 0;
for (int i = 0, l = 0; i < size(nums); ++i) {
++l;
if (i + 1 == size(nums) || !compare(nums[i], nums[i + 1])) {
result = max(result, l);
l = 0;
}
}
return result;
};
return max(f(less<int>()), f(greater<int>()));
}
};