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
}