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Read Integers from Space-Separated Input in Golang: An Efficient Approach
In programming, reading a set of integers separated by space from the standard input and storing them in an array efficiently is a common task. One way to achieve this is using a straightforward for loop. However, there exists a technique that leverages recursion to minimize the code while maintaining optimal performance.
Using Recursion Without Explicit Loops
The following Go code snippet demonstrates how to read integers from standard input without using for or goto loops:
<code class="go">package main import "fmt" func main() { var n int fmt.Println(`Enter the number of integers`) if _, err := fmt.Scan(&n); err != nil { panic(err) } fmt.Println(`Enter the integers`) all := make([]int, n) ReadN(all, 0, n) fmt.Println(all) } // Recursively reads n integers into all starting from position i. func ReadN(all []int, i, n int) { if n == 0 { return } if _, err := fmt.Scan(&all[i]); err != nil { panic(err) } ReadN(all, i+1, n-1) }</code>
Example Output
Suppose the standard input contains the integers:
Enter the number of integers 3 Enter the integers 23 45 66
Running the program would output:
[23 45 66]
Optimizing Input Scanning
To further optimize input scanning, consider replacing the fmt.Scan function in ReadN with a custom reader that enables faster input processing:
<code class="go">type reader struct { val int } func (r *reader) Read(b []byte) (int, error) { w, err := fmt.Scanf("%d", &r.val) if err != nil { return w, err } b[0] = byte(r.val) return 1, err }</code>
In this optimized implementation, a custom reader is created with a field val to hold the integer value. The Read method uses fmt.Scanf to read an integer from the standard input and store it in val. When reading from the custom reader, only one byte is processed, significantly reducing overhead.
By incorporating these techniques, you can efficiently read sets of integers from standard input in Golang, maximizing performance while minimizing code complexity.
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