Searching Algorithms

// Linear Search - O(n) time
public int linearSearch(int[] arr, int target) {
    for (int i = 0; i < arr.length; i++) {
        if (arr[i] == target) {
            return i;
        }
    }
    return -1; // Not found
}

// Linear Search with enhanced for loop
public int linearSearchEnhanced(int[] arr, int target) {
    for (int num : arr) {
        if (num == target) {
            return num; // Return the value if found
        }
    }
    return -1;
}

// Binary Search - O(log n) time (requires sorted array)
public int binarySearch(int[] arr, int target) {
    int left = 0;
    int right = arr.length - 1;
    
    while (left <= right) {
        int mid = left + (right - left) / 2;
        
        if (arr[mid] == target) {
            return mid;
        } else if (arr[mid] < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    
    return -1; // Not found
}

// Binary Search with recursion
public int binarySearchRecursive(int[] arr, int target, int left, int right) {
    if (left > right) {
        return -1;
    }
    
    int mid = left + (right - left) / 2;
    
    if (arr[mid] == target) {
        return mid;
    } else if (arr[mid] < target) {
        return binarySearchRecursive(arr, target, mid + 1, right);
    } else {
        return binarySearchRecursive(arr, target, left, mid - 1);
    }
}

// Find first occurrence of target
public int findFirstOccurrence(int[] arr, int target) {
    int left = 0;
    int right = arr.length - 1;
    int result = -1;
    
    while (left <= right) {
        int mid = left + (right - left) / 2;
        
        if (arr[mid] == target) {
            result = mid;
            right = mid - 1; // Continue searching left
        } else if (arr[mid] < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    
    return result;
}

// Find last occurrence of target
public int findLastOccurrence(int[] arr, int target) {
    int left = 0;
    int right = arr.length - 1;
    int result = -1;
    
    while (left <= right) {
        int mid = left + (right - left) / 2;
        
        if (arr[mid] == target) {
            result = mid;
            left = mid + 1; // Continue searching right
        } else if (arr[mid] < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    
    return result;
}