Unique Paths in Grid DP in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the DP array with zeros.

DSA Typescript

const dp: number[][] = Array(m).fill(0).map(() => Array(n).fill([1]));

Drag options to blanks, or click blank then click option'

Aundefined

B1

Cnull

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 0 initializes paths incorrectly.

Using null or undefined causes runtime errors.

We fill the DP array with zeros to start counting paths from zero.

2fill in blank

medium

Complete the code to set the starting point paths count to 1.

DSA Typescript

dp[0][0] = [1];

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A1

B0

C-1

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Setting starting point to 0 means no paths start there.

Using negative or null values causes errors.

The starting cell has exactly one path to itself.

3fill in blank

hard

Fix the error in the nested loops to correctly iterate over the grid.

DSA Typescript

for (let i = 0; i < [1]; i++) {
  for (let j = 0; j < n; j++) {
    if (i === 0 && j === 0) continue;
    dp[i][j] = (i > 0 ? dp[i - 1][j] : 0) + (j > 0 ? dp[i][j - 1] : 0);
  }
}

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Am

Bn

Cdp.length

Ddp[0].length

Attempts:

3 left

💡 Hint

Common Mistakes

Using n in outer loop causes index errors.

Using dp.length or dp[0].length may confuse rows and columns.

The outer loop should run from 0 to m (rows).

4fill in blank

hard

Fill both blanks to correctly return the total unique paths from top-left to bottom-right.

DSA Typescript

return dp[[1] - 1][[2] - 1];

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Am

Bn

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or 1 as indices returns wrong cell.

Swapping m and n causes wrong indexing.

The bottom-right cell is at index m-1, n-1 in the DP array.

5fill in blank

hard

Fill all three blanks to complete the function that calculates unique paths in an m x n grid.

DSA Typescript

function uniquePaths([1]: number, [2]: number): number {
  const dp: number[][] = Array([1]).fill(0).map(() => Array([2]).fill(0));
  dp[0][0] = 1;
  for (let i = 0; i < [1]; i++) {
    for (let j = 0; j < [2]; j++) {
      if (i === 0 && j === 0) continue;
      dp[i][j] = (i > 0 ? dp[i - 1][j] : 0) + (j > 0 ? dp[i][j - 1] : 0);
    }
  }
  return dp[[1] - 1][[2] - 1];
}

Drag options to blanks, or click blank then click option'

Am

Bn

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up m and n in parameters and array dimensions.

Using inconsistent variable names causes errors.

The function parameters and DP array dimensions use m and n consistently.