In this blog post, we will explore how to replace elements in a 2D vector using various methods and techniques. We will cover two common scenarios: replacing a single element at a given position, and replacing multiple elements based on certain criteria.

Scenario 1: Replacing a Single Element

To replace a single element in a 2D vector, we need to know the position of the element we want to replace. Let’s say we have a 2D vector called matrix of size m x n, and we want to replace the element at position (i, j) with a new value newVal.

Here’s an example in C++:

vector<vector<int>> matrix = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
};

// Replace element at position (1, 2) with a new value
int i = 1; // row index
int j = 2; // column index
int newVal = 10;

matrix[i][j] = newVal;

In this example, we have a 3x3 matrix and we want to replace the element at position (1, 2) with the value 10. By accessing the element using matrix[i][j], we can assign a new value to it.

Scenario 2: Replacing Multiple Elements

In some cases, we may want to replace multiple elements in a 2D vector based on certain criteria. For instance, let’s say we have a 2D vector matrix of size m x n, and we want to replace all occurrences of a specific value oldVal with a new value newVal.

Here’s an example in Python:

matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

oldVal = 2
newVal = 20

for row in matrix:
    for i in range(len(row)):
        if row[i] == oldVal:
            row[i] = newVal

In this example, we have a 3x3 matrix and we want to replace all occurrences of the value 2 with the value 20. We iterate over each row, and for each element in the row, we check if it matches the oldVal. If it does, we replace it with the newVal.

Conclusion

Replacing elements in a 2D vector can be done by accessing the specific position or by iterating over the vector and applying certain criteria. By understanding these techniques, you can easily replace elements in a 2D vector based on your needs.

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