learngo/16-slices/exercises/26-print-daily-requests/solution/main.go

// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
// For more tutorials  : https://learngoprogramming.com
// In-person training  : https://www.linkedin.com/in/inancgumus/
// Follow me on twitter: https://twitter.com/inancgumus

package main

import (
	"fmt"
	"strings"
)

func main() {
	// There are 3 request totals per day
	const N = 3

	// DAILY REQUESTS DATA (PER 8-HOUR)
	reqs := []int{
		500, 600, 250, // 1st day: 1350 requests
		200, 400, 50, // 2nd day: 650 requests
		900, 800, 600, // 3rd day: 2300 requests
		750, 250, 100, // 4th day: 1100 requests
		// grand total: 5400 requests
	}

	// ALSO TRY IT WITH THIS DATA:
	// reqs = []int{
	// 	500, 600, 250,
	// 	200, 400, 50,
	// 	900, 800, 600,
	// 	750, 250, 100,
	// 	150, 654, 235,
	// 	320, 534, 765,
	// 	121, 876, 285,
	// 	543, 642,
	// }

	// ================================================
	// Allocate a slice efficiently with the exact size needed.
	//
	// Find the `size` automatically using the `reqs` slice.
	// Do not type it manually.
	//
	l := len(reqs)
	size := l / N
	if l%N != 0 {
		size++
	}
	daily := make([][]int, 0, size)
	//
	// ================================================

	// ================================================
	// Group the `reqs` per day into the slice: `daily`.
	//
	// So the daily will be:
	// [
	//  [500, 600, 250]
	//  [200, 400, 50]
	//  [900, 800, 600]
	//  [750, 250, 100]
	// ]
	//
	for N <= len(reqs) {
		daily = append(daily, reqs[:N]) // append the daily requests
		reqs = reqs[N:]                 // move the slice pointer for the next day
	}

	// add the residual data
	if len(reqs) > 0 {
		daily = append(daily, reqs)
	}

	// ================================================

	// ================================================
	// Print the header
	fmt.Printf("%-10s%-10s\n", "Day", "Requests")
	fmt.Println(strings.Repeat("=", 20))

	// Print the data per day along with the totals
	var grand int

	for i, day := range daily {
		var sum int

		for _, req := range day {
			sum += req
			fmt.Printf("%-10d%-10d\n", i+1, req)
		}

		fmt.Printf("%9s %-10d\n\n", "TOTAL:", sum)

		grand += sum
	}

	fmt.Printf("%9s %-10d\n", "GRAND:", grand)
	// ================================================
}