lecture 01

args.cbool_fun.cLecture01.pdf

lecture 02 Bits and Bytes; Integer Representations

airline.cLecture02.pdf
![1BO2GXET{T]ECOZVB}F_~H.png


![N80F{3JRR4{R8P`V4PA5XW.png
![1KA4VPT)H{6QVS]T0GZ0HU.png
![K`F$PS96B8TY9LL32MIKCN.png

lecture 03 Bits and Bytes; Bitwise Operators

absolute_value.cabsolute_value_soln.cbits_playground.cbitvectors_masks.cbitvectors_masks_soln.ccolor_wheel.ccolor_wheel_soln.cis_power_of_2.cis_power_of_2_soln.cLecture03.pdflive_session.c
![EWZSXJLL[)XN(U)6P7YLPE.png

There are two kinds of right shifts, depending on the value and type you are
shifting:
• Logical Right Shift: fill new high-order bits with 0s.
• Arithmetic Right Shift: fill new high-order bits with the most-significant bit.
Unsigned numbers are right-shifted using Logical Right Shift.
Signed numbers are right-shifted using Arithmetic Right Shift.
This way, the sign of the number (if applicable) is preserved!
However, almost all compilers/machines use arithmetic, and you can most likely assume this. 几乎所有编译器都默认算术右移。

位操作实现绝对值函数

/* Bitwise version of absolute value with no conditionals or multiplication */
int absolute_value_bitwise(int value) {
    int sign = value >> (sizeof(int) * CHAR_BIT - 1);
    /*
     * When value is:
     * Nonnegative, value has 0 in MSB (sign bit), sign is all 0s (0)
     * Negative, value has 1 in MSB, sign is all 1s (-1)
     */
    return (value ^ sign) - sign;
    /* 
     * When val is nonnegative:
     * -- sign is 0. XOR with 0 keeps the same value (i.e. 1 ^ 0 == 1, 0 ^ 0 == 0)
     * -- (value ^ sign) == value. value - sign = value - 0 = value
     *
     * When value is negative:
     * -- sign bit pattern is all 1s. XOR with 1 flips bit (i.e. 0 ^ 1 == 1, 1 ^ 1 == 0)
     * -- (value ^ sign) == ~value
     * -- sign has numeric value of -1. y - sign == y + 1
     * -- (value ^ sign) - sign = ~value - sign = ~value + 1, which is the two's complement formula for -val
     */
}

位操作实现判断一个数是否是2的n次方

/* This function uses bitwise operators to return whether or not
 * this number is a power of 2. */
bool is_power_of_2(unsigned int value) {
      // TODO
      return value != 0 && (value & (value - 1)) == 0;
}

lecture 04

diamond.cdiamond_soln.cLecture04.pdflive_session.c

string

strlen函数计算字符数组的长度，不包括\0，时间复杂度为O(n)。








Both strcat and strncat remove the old ‘\0’ and add a new one at the end.





**
An array name (and a string name, by extension) is the address of the first element.