1 public class Solution { 2     public int maxEnvelopes(int[][] envelopes) { 3         if (envelopes.length < 2) { 4             return envelopes.length; 5         } 6          7         Arrays.sort(envelopes, new Comparator
     
      () { 8             @Override 9             public int compare(int[] a, int b[]) {10                 return Integer.compare(a[1], b[1]);11             }12         });13         14         int[] dp = new int[envelopes.length];15         int result = 1;16         for (int i = 0; i < envelopes.length; i++) {17             dp[i] = 1;18             for (int j = 0; j < i; j++) {19                 if (envelopes[i][0] > envelopes[j][0] &&20                     envelopes[i][1] > envelopes[j][1]) {21                         dp[i] = Math.max(dp[i], dp[j] + 1);22                     }23             }24             result = Math.max(dp[i], result);25         }26         return result;27     }28 }
     

Last DP element MAY NOT be the answer since the max number can happened between.