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Which of the following expressions is equivalent to !(c || d) ?

直接应用德摩根定律。
1

Which of the following is equivalent to the code segment below?

if (x > 2) x = x * 2;
if (x > 4) x = 0;
注意当x变为自身的两倍以后,两个if语句条件是等价的。在都会被执行的前提下,x的最终结果是最后一个if所决定的。
3

Which of the following is equivalent to the code segment below?

if (x > 0) x = -x;
if (x < 0) x = 0;
无论x是正数、负数还是零,最终结果都会被清零。
1

At a certain high school students receive letter grades based on the following scale.

Integer Score Letter Grade
93 or above A
From 84 to 92 inclusive B
From 75 to 83 inclusive C
Below 75 F

Which of the following code segments will assign the correct string to grade for a given integer score?
I.

if (score >= 93) grade = "A";
if (score >= 84 && score <= 92) grade = "B";
if (score >= 75 && score <= 83) grade = "C";
if (score < 75) grade = "F";

II.

if (score >= 93)
 grade = "A";
if (score >= 84)
 grade = "B";
if (score >=75)
 grade = "C";
if (score < 75)
 grade = "F";

III.

if (score >= 93) grade = "A";
else if (score >= 84) grade = "B";
else if (score >= 75) grade = "C";
else grade = "F";
II是错的,对于高分后面的if也同样成立,会把grade给覆盖掉。注意到III的else if隐式的包含了上一步条件的否定。
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陈 欣

AADPS创始人

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