Golang | Leetcode Golang题解之第241题为运算表达式设计优先级

题目：

题解：

const addition, subtraction, multiplication = -1, -2, -3
 
func diffWaysToCompute(expression string) []int {
    ops := []int{}
    for i, n := 0, len(expression); i < n; {
        if unicode.IsDigit(rune(expression[i])) {
            x := 0
            for ; i < n && unicode.IsDigit(rune(expression[i])); i++ {
                x = x*10 + int(expression[i]-'0')
            }
            ops = append(ops, x)
        } else {
            if expression[i] == '+' {
                ops = append(ops, addition)
            } else if expression[i] == '-' {
                ops = append(ops, subtraction)
            } else {
                ops = append(ops, multiplication)
            }
            i++
        }
    }
 
    n := len(ops)
    dp := make([][][]int, n)
    for i, x := range ops {
        dp[i] = make([][]int, n)
        dp[i][i] = []int{x}
    }
    for sz := 3; sz <= n; sz++ {
        for l, r := 0, sz-1; r < n; l += 2 {
            for k := l + 1; k < r; k += 2 {
                for _, x := range dp[l][k-1] {
                    for _, y := range dp[k+1][r] {
                        if ops[k] == addition {
                            dp[l][r] = append(dp[l][r], x+y)
                        } else if ops[k] == subtraction {
                            dp[l][r] = append(dp[l][r], x-y)
                        } else {
                            dp[l][r] = append(dp[l][r], x*y)
                        }
                    }
                }
            }
            r += 2
        }
    }
    return dp[0][n-1]
}