Final Value of Variable After Performing Operations

Final Value of Variable After Performing Operations - Problem

Imagine you're building a simple interpreter for a minimalist programming language! This language has only one variable X (initially set to 0) and supports just four operations:

++X and X++ - both increment X by 1
--X and X-- - both decrement X by 1

Given an array of strings operations containing a sequence of these operations, your task is to simulate the execution and return the final value of X after performing all operations.

Note: In this simplified language, there's no difference between pre-increment (++X) and post-increment (X++) - they both just add 1 to X. Same applies to decrement operations.

Input & Output

example_1.py — Basic Operations

$ Input: operations = ["--X", "X++", "X++"]

› Output: 1

💡 Note: Starting with X = 0: --X makes X = -1, then X++ makes X = 0, then X++ makes X = 1. Final result is 1.

example_2.py — All Increments

$ Input: operations = ["++X", "++X", "X++"]

› Output: 3

💡 Note: Starting with X = 0: ++X makes X = 1, ++X makes X = 2, X++ makes X = 3. All operations increment X.

example_3.py — Single Operation

$ Input: operations = ["X++"]

› Output: 1

💡 Note: Starting with X = 0, the single operation X++ increments X to 1.

Visualization

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Understanding the Visualization

Start Fresh

Calculator display shows 0

Press Buttons

Each operation is like pressing +1 or -1 button

Read Display

The final number on the display is your answer

Key Takeaway

🎯 Key Insight: This is a straightforward simulation problem - just process each operation sequentially and keep track of the running total!

Time & Space Complexity

Time Complexity

⏱️

O(n)

We iterate through the operations array once, where n is the number of operations

✓ Linear Growth

Space Complexity

O(1)

We only use a constant amount of extra space to store the variable X

✓ Linear Space

Constraints

1 ≤ operations.length ≤ 100
operations[i] will be either "++X", "X++", "--X", or "X--"
Note: The final value of X is guaranteed to fit in a 32-bit signed integer

Asked in

a Amazon 15 G Google 12 ⊞ Microsoft 8 f Meta 5

This problem is a simple simulation task. The optimal approach is to iterate through each operation once and update the variable X accordingly. Since we only need to distinguish between increment (+) and decrement (-) operations, we can check for the presence of '+' or '-' characters in each operation string. The time complexity is O(n) where n is the number of operations, and space complexity is O(1).

Common Approaches

Approach	Time	Space	Notes
✓ Simulation Approach	O(n)	O(1)	Iterate through each operation and update the variable X accordingly

Simulation Approach — Algorithm Steps

Initialize variable X to 0
Iterate through each operation in the operations array
For each operation, check if it contains '+' or '-'
If it contains '+', increment X by 1
If it contains '-', decrement X by 1
Return the final value of X

Visualization

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Step-by-Step Walkthrough

Initialize

Start with X = 0

Process Operations

Go through each operation and update X

Return Result

Return the final value of X

Code -

solution.c — C

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int finalValueAfterOperations(char** operations, int operationsSize) {
    int X = 0;
    for (int i = 0; i < operationsSize; i++) {
        if (strstr(operations[i], "+") != NULL) {
            X += 1;
        } else { // strstr(operations[i], "-") != NULL
            X -= 1;
        }
    }
    return X;
}

int main() {
    char* operations[] = {"--X", "X++", "X++"}; // Example input
    int size = 3;
    printf("%d\n", finalValueAfterOperations(operations, size));
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

We iterate through the operations array once, where n is the number of operations

✓ Linear Growth

Space Complexity

O(1)

We only use a constant amount of extra space to store the variable X

✓ Linear Space

Constraints

1 ≤ operations.length ≤ 100
operations[i] will be either "++X", "X++", "--X", or "X--"
Note: The final value of X is guaranteed to fit in a 32-bit signed integer

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Input & Output

Visualization

Time & Space Complexity

Related Problems

Constraints

Common Approaches

Simulation Approach — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Constraints

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