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646. Maximum Length of Pair Chain 👍

  • Time: $O(\texttt{sort})$
  • Space: $O(\texttt{sort})$
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class Solution {
 public:
  int findLongestChain(vector<vector<int>>& pairs) {
    int ans = 0;
    int prevEnd = INT_MIN;

    ranges::sort(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;
  }
};

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import java.util.Arrays;

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

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

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

    return ans;
  }
}

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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