Palindrome Partitioning DP Minimum Cuts in DSA Javascript - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of minimum cuts for palindrome partitioning

What is the output of the following JavaScript code that calculates the minimum cuts needed to partition the string into palindromes?

DSA Javascript

function minCut(s) {
  const n = s.length;
  const dp = new Array(n).fill(0);
  const palindrome = Array.from({ length: n }, () => new Array(n).fill(false));

  for (let end = 0; end < n; end++) {
    let minCuts = end;
    for (let start = 0; start <= end; start++) {
      if (s[start] === s[end] && (end - start < 2 || palindrome[start + 1][end - 1])) {
        palindrome[start][end] = true;
        minCuts = start === 0 ? 0 : Math.min(minCuts, dp[start - 1] + 1);
      }
    }
    dp[end] = minCuts;
  }
  return dp[n - 1];
}

console.log(minCut("aab"));

A 2

B 1

C 0

D 3

💡 Hint

Think about how many cuts are needed to split "aab" into palindromes.

The string "aab" can be split into "aa" and "b", both palindromes, with only 1 cut needed.

🧠 Conceptual

intermediate

Understanding the palindrome table in DP

In the palindrome partitioning DP solution, what does the 2D boolean array 'palindrome' represent?

A It stores whether the substring from index i to j is a palindrome.

B It stores the count of palindrome substrings between i and j.

C It stores the length of the longest palindrome substring ending at j.

D It stores the minimum cuts needed for substring from i to j.

💡 Hint

Think about what information helps decide if a substring is palindrome quickly.

The 'palindrome' array marks true if substring s[i..j] is palindrome, which helps avoid recomputation.

❓ Predict Output

advanced

Output of minimum cuts for a complex string

What is the output of the following code for the input string "abccbc"?

DSA Javascript

function minCut(s) {
  const n = s.length;
  const dp = new Array(n).fill(0);
  const palindrome = Array.from({ length: n }, () => new Array(n).fill(false));

  for (let end = 0; end < n; end++) {
    let minCuts = end;
    for (let start = 0; start <= end; start++) {
      if (s[start] === s[end] && (end - start < 2 || palindrome[start + 1][end - 1])) {
        palindrome[start][end] = true;
        minCuts = start === 0 ? 0 : Math.min(minCuts, dp[start - 1] + 1);
      }
    }
    dp[end] = minCuts;
  }
  return dp[n - 1];
}

console.log(minCut("abccbc"));

A 1

B 0

C 2

D 3

💡 Hint

Try to find palindrome partitions with minimum cuts.

The string "abccbc" can be partitioned as "a" | "bccb" | "c" with 2 cuts.

🔧 Debug

advanced

Identify the error in the DP palindrome partitioning code

What error will the following code produce when run?

DSA Javascript

function minCut(s) {
  const n = s.length;
  const dp = new Array(n).fill(0);
  const palindrome = Array.from({ length: n }, () => new Array(n).fill(false));

  for (let end = 0; end < n; end++) {
    let minCuts = end;
    for (let start = 0; start <= end; start++) {
      if (s[start] === s[end] && (end - start < 2 || palindrome[start + 1][end - 1])) {
        palindrome[start][end] = true;
        minCuts = start === 0 ? 0 : Math.min(minCuts, dp[start - 1] + 1);
      }
    }
    dp[end] = minCuts;
  }
  return dp[n - 1];
}

console.log(minCut("abc"));

A Wrong output: 1 instead of 2

B TypeError: Cannot read property 'length' of undefined

C ReferenceError: dp is not defined

D SyntaxError: Unexpected token

💡 Hint

Check the index used to access dp array inside the inner loop.

The code uses dp[start] instead of dp[start - 1], causing wrong minimum cuts calculation.

🧠 Conceptual

expert

Time complexity of palindrome partitioning minimum cuts DP

What is the time complexity of the dynamic programming solution for palindrome partitioning minimum cuts?

A O(n)

B O(n log n)

C O(n^3)

D O(n^2)

💡 Hint

Consider the total number of iterations in the nested loops.

The solution uses two nested loops totaling O(n^2) iterations with O(1) work inside, resulting in quadratic time complexity.

Practice

1. What does the term minimum cuts mean in the context of palindrome partitioning?

easy

A. The number of characters to remove to make the string a palindrome

B. The longest palindrome substring in the string

C. The total number of palindromic substrings in the string

D. The smallest number of cuts needed to split the string into palindromic substrings

Solution

1. Step 1: Understand palindrome partitioning

   Palindrome partitioning splits a string into substrings where each substring is a palindrome.

2. Step 2: Define minimum cuts

   Minimum cuts means the least number of cuts needed to divide the string so that every part is a palindrome.

3. Final Answer:

   The smallest number of cuts needed to split the string into palindromic substrings -> Option D

4. Quick Check:

   Minimum cuts = smallest cuts for palindrome parts [OK]

Hint: Minimum cuts split string into palindrome parts with fewest cuts [OK]

Common Mistakes:

• Confusing minimum cuts with longest palindrome substring
• Thinking minimum cuts count characters removed
• Mixing total palindrome substrings with minimum cuts

2. Which of the following is the correct way to initialize a 2D boolean array isPalindrome for a string s of length n in JavaScript?

easy

A. const isPalindrome = Array.from({length: n}, () => Array(n).fill(false));

B. const isPalindrome = Array(n).fill(Array(n).fill(false));

C. const isPalindrome = new Array(n).fill(new Array(n).fill(false));

D. const isPalindrome = Array(n).map(Array(n).fill(false));

Solution

1. Step 1: Understand 2D array initialization in JavaScript

   Using Array.from with a mapping function creates independent inner arrays.

2. Step 2: Compare options

   const isPalindrome = Array.from({length: n}, () => Array(n).fill(false)); correctly creates separate inner arrays filled with false. Options A and C create references to the same inner array, causing bugs. const isPalindrome = Array(n).map(() => Array(n).fill(false)); fails because map on uninitialized array does not work as expected.

3. Final Answer:

   const isPalindrome = Array.from({length: n}, () => Array(n).fill(false)); -> Option A

4. Quick Check:

   Use Array.from with function for independent inner arrays [OK]

Hint: Use Array.from with function to avoid shared references [OK]

Common Mistakes:

• Using fill with array directly causing shared references
• Using map on uninitialized arrays
• Not initializing inner arrays separately

3. What is the output of the following code snippet for s = "aab"?

function minCut(s) {
  const n = s.length;
  const isPalindrome = Array.from({length: n}, () => Array(n).fill(false));
  for (let i = 0; i < n; i++) {
    isPalindrome[i][i] = true;
  }
  for (let length = 2; length <= n; length++) {
    for (let start = 0; start <= n - length; start++) {
      let end = start + length - 1;
      if (s[start] === s[end]) {
        if (length === 2) {
          isPalindrome[start][end] = true;
        } else {
          isPalindrome[start][end] = isPalindrome[start + 1][end - 1];
        }
      }
    }
  }
  const cuts = Array(n).fill(0);
  for (let i = 0; i < n; i++) {
    let minCut = i;
    for (let j = 0; j <= i; j++) {
      if (isPalindrome[j][i]) {
        minCut = j === 0 ? 0 : Math.min(minCut, cuts[j - 1] + 1);
      }
    }
    cuts[i] = minCut;
  }
  return cuts[n - 1];
}
console.log(minCut(s));

medium

A. 0

B. 1

C. 2

D. 3

Solution

1. Step 1: Identify palindromic substrings in "aab"

   "a", "a", "b" are palindromes; "aa" is palindrome; "aab" is not.

2. Step 2: Calculate minimum cuts

   Minimum cuts needed: split "aab" as "aa" | "b" with 1 cut.

3. Final Answer:

   1 -> Option B

4. Quick Check:

   Minimum cuts for "aab" = 1 [OK]

Hint: Check palindrome substrings, then find fewest cuts [OK]

Common Mistakes:

• Assuming no cuts needed for non-palindrome string
• Counting total palindromic substrings instead of cuts
• Misindexing palindrome checks

4. The following code attempts to compute minimum cuts for palindrome partitioning but has a bug. What is the error?

function minCut(s) {
  const n = s.length;
  const isPalindrome = Array(n).fill(Array(n).fill(false));
  for (let i = 0; i < n; i++) {
    isPalindrome[i][i] = true;
  }
  // ... rest of palindrome logic ...
  return 0;
}

medium

A. The function does not return the minimum cuts value

B. Loop for setting isPalindrome[i][i] should start from 1, not 0

C. isPalindrome initialization shares inner arrays causing incorrect updates

D. The string length n is not calculated correctly

Solution

1. Step 1: Analyze isPalindrome array initialization

   Using fill with an array creates references to the same inner array, so updating one row updates all rows.

2. Step 2: Understand impact on palindrome checks

   This causes incorrect palindrome marking because all rows share the same inner array, corrupting data.

3. Final Answer:

   isPalindrome initialization shares inner arrays causing incorrect updates -> Option C

4. Quick Check:

   Shared inner arrays cause bugs in 2D boolean array [OK]

Hint: Avoid fill with arrays; use Array.from with function [OK]

Common Mistakes:

• Ignoring shared reference problem in 2D arrays
• Thinking loop start index causes bug
• Overlooking missing return value as main error

5. Given the string s = "ababbbabbababa", what is the minimum number of cuts needed to partition it into palindromic substrings using dynamic programming?

hard

A. 3

B. 5

C. 4

D. 6

Solution

1. Step 1: Understand palindrome partitions for "ababbbabbababa"

   This string can be partitioned into palindromes with minimum cuts by checking all substrings and using DP to find minimal cuts.

2. Step 2: Use known result or DP approach

   The minimum cuts for this string is 3, as it can be split into palindromic parts like "a|babbbab|b|ababa" or similar partitions.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Minimum cuts for complex palindrome string = 3 [OK]

Hint: Use DP palindrome checks and cuts array to find minimum cuts [OK]

Common Mistakes:

• Assuming minimum cuts equals number of palindromic substrings
• Miscounting cuts by off-by-one errors
• Not considering overlapping palindrome substrings