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Problem solution · Java

Split Message Based on Limit

Split Message Based on Limit: a Java solution using direct simulation. Learn the idea, check the complexity, and read the full code, with credit to walkccc LeetCode Solutions.

Technique
Direct simulation
Source
walkccc LeetCode Solutions
Length
35 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Direct simulation

For Split Message Based on Limit, the implementation follows the problem’s operations directly while maintaining only the state needed for the next decision.

  1. Translate each rule into one explicit state update.
  2. Maintain the invariant after every processed item.
  3. Return the accumulated state once all relevant input has been handled.

Code notes

  • 35 lines of Java from the credited upstream file 2468.java.
  • The implementation visibly relies on sequence storage.
  • 2 loop blocks detected.

Complexity

Count the number and nesting of passes over the input, then include the maintained containers in the memory estimate.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from walkccc LeetCode Solutions by P.-Y. Chen (walkccc) and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeSplit Message Based on Limit · JavaJava
Use this to learn the idea, then write your own version.
class Solution {  public String[] splitMessage(String message, int limit) {    final int MESSAGE_LENGTH = message.length();    int b = 1;    // the total length of a: initialized with the length of "1"    int aLength = sz(1);     // the total length of b := b * sz(b)    // The total length of "</>" := b * 3    while (b * limit < b * (sz(b) + 3) + aLength + MESSAGE_LENGTH) {      // If the length of the last suffix "<b/b>" := sz(b) * 2 + 3 >= limit,      // then it's impossible that the length of "*<b/b>" <= limit.      if (sz(b) * 2 + 3 >= limit)        return new String[] {};      aLength += sz(++b);    }     String[] ans = new String[b];     for (int i = 0, a = 1; a <= b; ++a) {      // the length of "<a/b>" := sz(a) + sz(b) + 3      final int j = limit - (sz(a) + sz(b) + 3);      ans[a - 1] = message.substring(i, Math.min(message.length(), i + j)) + "<" +                   String.valueOf(a) + "/" + String.valueOf(b) + ">";      i += j;    }     return ans;  }   private int sz(int num) {    return String.valueOf(num).length();  }}

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