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LeetCode Solutions

646. Maximum Length of Pair Chain

Time: $O(n\log n)$

Space: $O(1)$

			


class Solution {
 public:
  int findLongestChain(vector<vector<int>>& pairs) {
    int ans = 0;
    int prevEnd = INT_MIN;

    sort(begin(pairs), end(pairs),
         [](const auto& a, const auto& b) { return a[1] < b[1]; });

    for (const vector<int>& pair : pairs)
      if (pair[0] > prevEnd) {
        ++ans;
        prevEnd = pair[1];
      }

    return ans;
  }
};




			


import java.util.Arrays;

class Solution {
  public int findLongestChain(int[][] pairs) {
    int ans = 0;
    int prevEnd = Integer.MIN_VALUE;

    Arrays.sort(pairs, (a, b) -> a[1] - b[1]);

    for (int[] pair : pairs)
      if (pair[0] > prevEnd) {
        ++ans;
        prevEnd = pair[1];
      }

    return ans;
  }
}




			


class Solution:
  def findLongestChain(self, pairs: List[List[int]]) -> int:
    ans = 0
    prevEnd = -math.inf

    for s, e in sorted(pairs, key=lambda x: x[1]):
      if s > prevEnd:
        ans += 1
        prevEnd = e

    return ans