leetcode——334—— Increasing Triplet Subsequence

Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array.

Formally the function should:

Return true if there exists i, j, k
such that arr[i] < arr[j] < arr[k] given 0 ≤ i < j < k ≤ n-1 else return false.

Your algorithm should run in O(n) time complexity and O(1) space complexity.

Examples:
Given [1, 2, 3, 4, 5],
return true.

Given [5, 4, 3, 2, 1],
return false.

class Solution {
public:
    bool increasingTriplet(vector<int>& nums) {
        int c1 = INT_MAX;
        int c2 = INT_MAX;
        for(int x = 0; x < nums.size(); x++){
            if(nums[x] <= c1){
                c1 = nums[x]; 
            }
            else if(nums[x] <= c2){
                c2 = nums[x];
            }
            else{
                return true;
            }
        }
        return false;

    }
};