我要找到最大的用户，但有一些限制提供了三个号码。它不允许使用任何条件语句。我试着用三元操作符象下面这样。

I have to find maximum of three number provided by user but with some restrictions. Its not allowed to use any conditional statement. I tried using ternary operator like below.

max=(a>b?a:b)>c?(a>b?a:b):c

但同样它仅限于使用三元运算符。 现在，我没有得到任何想法如何做到这一点？

But again its restricted to use ternary operator. Now I am not getting any idea how to do this?

推荐答案

发生短路布尔EX pressions趁着：

Taking advantage of short-circuiting in boolean expressions:

int max(int a, int b, int c)
{
     int m = a;
     (m < b) && (m = b); //these are not conditional statements.
     (m < c) && (m = c); //these are just boolean expressions.
     return m;
}

说明：

在布尔和的操作，如 X - 安培;＆安培;是，计算y 当且仅当 X 是真实的。如果 X 为假，则是不计算，因为整个EX pression是false，这可以推断甚至没有评估是。这就是所谓的短路时，可以不评估所有的操作数在其推断的布尔EX pression的价值。

In boolean AND operation such as x && y, y is evaluated if and only if x is true. If x is false, then y is not evaluated, because the whole expression would be false which can be deduced without even evaluating y. This is called short-circuiting when the value of a boolean expression can be deduced without evaluating all operands in it.

将这一原则上述code。最初 M 是 A 。现在，如果（M＆LT; B）是真实的，那么这意味着， B 大于 M （这实际上是 A ），所以第二个SUBEX pression （M = B）评估和 M 设置为 B 。然而，如果（M＆LT; B）为假，则第二SUBEX pression将不进行评估， M 仍将 A （大于 B ）。以类似的方式，第二前pression评估（下一行）。

Apply this principle to the above code. Initially m is a. Now if (m < b) is true, then that means, b is greater than m (which is actually a), so the second subexpression (m = b) is evaluated and m is set to b. If however (m < b) is false, then second subexpression will not be evaluated and m will remain a (which is greater than b). In a similar way, second expression is evaluated (on the next line).

总之，你可以阅读EX pression （M＆LT，X）及和放大器; （M = X）如下：设置 M 到 X 如果和只有当 M 比 X小于即（M＆LT; X） 是真实的。希望这有助于你了解code。

In short, you can read the expression (m < x) && (m = x) as follows : set m to x if and only if m is less than x i.e (m < x) is true. Hope this helps you understanding the code.

测试code：

int main() {
        printf("%d\n", max(1,2,3));
        printf("%d\n", max(2,3,1));
        printf("%d\n", max(3,1,2));
        return 0;
}

输出：

3
3
3

在线演示： http://www.ideone.com/8045P

请注意实施最高给出警告，因为评估EX pressions不使用：

Note the implementation of max gives warnings because evaluated expressions are not used:

prog.c中：6：警告：价值计算，不使用   prog.c中：7：警告：未使用的价值计算

prog.c:6: warning: value computed is not used prog.c:7: warning: value computed is not used

要避免这些（无害的）警告，可以实现最高为：

To avoid these (harmless) warnings, you can implement max as:

int max(int a, int b, int c)
{
     int m = a;
     (void)((m < b) && (m = b)); //these are not conditional statements.
     (void)((m < c) && (m = c)); //these are just boolean expressions.
     return m;
}

诀窍是，现在我们casting布尔EX pressions到无效，这将导致SUP $ P $的警告pssion 的：

The trick is that now we're casting the boolean expressions to void, which causes suppression of the warnings: