Python: Find the indices of all occurrences of target in the uneven matrix

Python Programming Puzzles: Exercise-18 with Solution

An irregular/uneven matrix, or ragged matrix, is a matrix that has a different number of elements in each row. Ragged matrices are not used in linear algebra, since standard matrix transformations cannot be performed on them, but they are useful as arrays in computing.

Write a Python program to find the indices of all occurrences of target in the uneven matrix.

Input:
[([1, 3, 2, 32, 19], [19, 2, 48, 19], [], [9, 35, 4], [3, 19]), 19]
Output:
[[0, 4], [1, 0], [1, 3], [4, 1]]

Input:
[([1, 2, 3, 2], [], [7, 9, 2, 1, 4]),2]
Output:
[[0, 1], [0, 3], [2, 2]]

Pictorial Presentation:

Sample Solution-1:

Python Code:

def test(M, T):
    return [[i, j] for i, row in enumerate(M) for j, n in enumerate(row) if n == T]
M = [[1, 3, 2, 32, 19], [19, 2, 48, 19], [], [9, 35, 4], [3, 19]]
T = 19
print("Matrix:")
print(M)
print("Target value:")
print(T)
print("Indices of all occurrences of the target value in the said uneven matrix:")
print(test(M,T))
 
M = [[1, 2, 3, 2], [], [7, 9, 2, 1, 4]]
T = 2
print("\nMatrix:")
print(M)
print("Target value:")
print(T)
print("Indices of all occurrences of the target value in the said uneven matrix:")
print(test(M,T)) 

Sample Output:

Matrix:
[[1, 3, 2, 32, 19], [19, 2, 48, 19], [], [9, 35, 4], [3, 19]]
Target value:
19
Indices of all occurrences of the target value in the said uneven matrix:
[[0, 4], [1, 0], [1, 3], [4, 1]]

Matrix:
[[1, 2, 3, 2], [], [7, 9, 2, 1, 4]]
Target value:
2
Indices of all occurrences of the target value in the said uneven matrix:
[[0, 1], [0, 3], [2, 2]]

Flowchart:

Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:

Sample Solution-2:

Python Code:

#License: https://bit.ly/3oLErEI

def test(M, T):
    indices = []
    for i, num in enumerate(M[0]):
        if num == T:
            indices.append([0, i])
    # Search for element starting from the first column and storing the indices of the found elements in a list
    for row, row_num in zip(M[1:], range(1, len(M))):
        for i, num in enumerate(row):
            if num == T:
                indices.append([row_num, i])
    return indices

M = [[1, 3, 2, 32, 19], [19, 2, 48, 19], [], [9, 35, 4], [3, 19]]
T = 19
print("Matrix:")
print(M)
print("Target value:")
print(T)
print("Indices of all occurrences of the target value in the said uneven matrix:")
print(test(M,T))
 
M = [[1, 2, 3, 2], [], [7, 9, 2, 1, 4]]
T = 2
print("\nMatrix:")
print(M)
print("Target value:")
print(T)
print("Indices of all occurrences of the target value in the said uneven matrix:")
print(test(M,T))

Sample Output:

Matrix:
[[1, 3, 2, 32, 19], [19, 2, 48, 19], [], [9, 35, 4], [3, 19]]
Target value:
19
Indices of all occurrences of the target value in the said uneven matrix:
[[0, 4], [1, 0], [1, 3], [4, 1]]

Matrix:
[[1, 2, 3, 2], [], [7, 9, 2, 1, 4]]
Target value:
2
Indices of all occurrences of the target value in the said uneven matrix:
[[0, 1], [0, 3], [2, 2]]

Flowchart:

Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:

Python Code Editor :

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