lavos/cap3/ex34.go

package cap3

import "fmt"

const (
	_opAdd   = '+' // 加
	_opMinus = '-' // 减
	_opMulti = '*' // 乘
	_opDiv   = '/' // 除
)

var allOperations = [4]byte{_opAdd, _opMinus, _opMulti, _opDiv}

func Ex34(x1, x2, x3, x4, x5, y int) []string {
	result := make([]string, 0)
	operations := make([]byte, 4)
	nums := [5]int{x1, x2, x3, x4, x5}

	// 一层一层尝试运算符
	for _, operations[0] = range allOperations {
		// 当前为除法，判断下一个数是否为0，如果是则直接跳过，下同
		if operations[0] == _opDiv && nums[1] == 0 {
			continue
		}
		for _, operations[1] = range allOperations {
			if operations[1] == _opDiv && nums[2] == 0 {
				continue
			}
			for _, operations[2] = range allOperations {
				if operations[2] == _opDiv && nums[3] == 0 {
					continue
				}
				for _, operations[4] = range allOperations {
					if operations[4] == _opDiv && nums[4] == 0 {
						continue
					}

					// 计算表达式
					p, f, q := 0, 1, nums[1]
					for i, op := range operations {
						switch op {
						case _opAdd:
							p += f * q
							f, q = 1, nums[i+1]
						case _opMinus:
							p += f * q
							f, q = -1, nums[i+1]
						case _opMulti:
							q *= nums[i+1]
						case _opDiv:
							q /= nums[i+1]
						}
					}

					// 结果等于给定的数字y，添加到结果集中
					if p+f*q == y {
						text := ""
						for _, num := range nums {
							text += fmt.Sprintf("%d %c ", num, operations)
						}

						text += fmt.Sprintf("%d = %d\n", nums[4], y)
						result = append(result, text)
					}
				}
			}
		}
	}

	return result
}