Window Sliding Technique in C

The sliding window technique is a common algorithmic approach used to solve problems that involve subarrays or subsequences of a given array or string. It is especially useful when you need to efficiently track and update a subset of elements within a larger data structure while iterating through it.

Here’s a simple C program that demonstrates the sliding window technique for finding the maximum sum of a subarray of a fixed size k within an array:

#include <stdio.h>

// Function to find the maximum sum of a subarray of size k
int maxSumSubarray(int arr[], int n, int k) {
    int maxSum = 0;
    int currentSum = 0;

    // Calculate the sum of the first k elements
    for (int i = 0; i < k; i++) {
        currentSum += arr[i];
    }

    maxSum = currentSum;

    // Slide the window and update the sums
    for (int i = k; i < n; i++) {
        currentSum += arr[i] - arr[i - k];
        if (currentSum > maxSum) {
            maxSum = currentSum;
        }
    }

    return maxSum;
}

int main() {
    int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
    int n = sizeof(arr) / sizeof(arr[0]);
    int k = 3;

    int maxSum = maxSumSubarray(arr, n, k);

    printf("Maximum sum of a subarray of size %d is: %d\n", k, maxSum);

    return 0;
}

In this program:

• We define the maxSumSubarray function, which takes an array arr, its size n, and the subarray size k as parameters.
• We initialize maxSum and currentSum to 0.
• We calculate the sum of the first k elements in the array and store it in currentSum.
• We set maxSum to currentSum.
• We then slide the window from index k to n-1, updating currentSum by subtracting the element that goes out of the window and adding the new element that enters the window.
• We keep track of the maximum sum found in maxSum.
• Finally, we return maxSum.

In the main function, we call maxSumSubarray with a sample array and subarray size and print the maximum sum.

You can modify this program to solve other sliding window problems by adapting the logic inside the maxSumSubarray function.