Description
Given an integer array nums, return true if there exists a triple of indices (i, j, k) such that i < j < k and nums[i] < nums[j] < nums[k]. If no such indices exists, return false.
Example 1:
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| Input: nums = [1,2,3,4,5]
Output: true
Explanation: Any triplet where i < j < k is valid.
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Example 2:
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| Input: nums = [5,4,3,2,1]
Output: false
Explanation: No triplet exists.
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Example 3:
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| Input: nums = [2,1,5,0,4,6]
Output: true
Explanation: The triplet (3, 4, 5) is valid because nums[3] == 0 < nums[4] == 4 < nums[5] == 6.
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Constraints:
1 <= nums.length <= 5 * 10^5-2^31 <= nums[i] <= 2^31 - 1
Solutions
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| class Solution {
public:
bool increasingTriplet(vector<int>& nums) {
if (nums.size() < 3) {
return false;
}
int first = nums[0];
int second = std::numeric_limits<int>::max();
for (int i = 1; i < nums.size(); i++) {
// third is greater than second
if (nums[i] > second) {
return true;
}
// third is less than second，but greate than first
else if (nums[i] > first) {
second = nums[i];
}
// third is less than first
else {
first = nums[i];
}
}
return false;
}
};
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