C++ 运算符详解

运行结果

=== 算术运算符示例 ===
a = 10, b = 3
a + b = 13
a - b = 7
a * b = 30
a / b = 3
x / y = 3.33333
a % b = 1
=== 自增自减运算符 ===
初始值 c = 5
c++ = 5
现在 c = 6
++c = 7
现在 c = 7
c-- = 7
现在 c = 6
--c = 5
现在 c = 5

2. 关系运算符

功能

用于比较两个值，返回布尔值（true/false）。

代码示例

#include <iostream>
using namespace std;

int main() {
    cout << "=== 关系运算符示例 ===" << endl;
    int a = 10, b = 20, c = 10;
    cout << "a = " << a << ", b = " << b << ", c = " << c << endl << endl;

    // 等于和不等于
    cout << "a == b: " << (a == b) << endl;       // 等于比较
    cout << "a == c: " << (a == c) << endl;       // 等于比较
    cout << "a != b: " << (a != b) << endl;       // 不等于比较
    cout << "a != c: " << (a != c) << endl;       // 不等于比较

    cout << endl;
    // 大小比较
    cout << "a > b: " << (a > b) << endl;         // 大于比较
    cout << "a < b: " << (a < b) << endl;         // 小于比较
    cout << "a >= c: " << (a >= c) << endl;       // 大于等于比较
    cout << "a <= c: " << (a <= c) << endl;       // 小于等于比较
    cout << "b >= a: " << (b >= a) << endl;       // 大于等于比较

    cout << endl << "=== 在条件语句中使用 ===" << endl;
    // 在 if 语句中使用关系运算符
    if (a < b) {
        cout << "a 小于 b" << endl;
    }
    if (a == c) {
        cout << "a 等于 c" << endl;
    }
    if (b > a) {
        cout << "b 大于 a" << endl;
    }
    return 0;
}

运行结果

=== 关系运算符示例 ===
a = 10, b = 20, c = 10
a == b: 0
a == c: 1
a != b: 1
a != c: 0
a > b: 0
a < b: 1
a >= c: 1
a <= c: 1
b >= a: 1
=== 在条件语句中使用 ===
a 小于 b
a 等于 c
b 大于 a

3. 逻辑运算符

功能

用于组合多个条件，返回布尔值。

代码示例

#include <iostream>
using namespace std;

int main() {
    cout << "=== 逻辑运算符示例 ===" << endl;
    bool trueVal = true, falseVal = false;
    int age = 25;
    double salary = 50000.0;
    bool hasLicense = true;

    cout << "trueVal = " << trueVal << ", falseVal = " << falseVal << endl;
    cout << "age = " << age << ", salary = " << salary << ", hasLicense = " << hasLicense << endl << endl;

    // 逻辑与 (&&) - 两个条件都为真时返回真
    cout << "trueVal && falseVal: " << (trueVal && falseVal) << endl;
    cout << "trueVal && trueVal: " << (trueVal && trueVal) << endl;
    cout << "(age >= 18) && (hasLicense): " << ((age >= 18) && hasLicense) << endl;

    cout << endl;
    // 逻辑或 (||) - 至少一个条件为真时返回真
    cout << "trueVal || falseVal: " << (trueVal || falseVal) << endl;
    cout << "falseVal || falseVal: " << (falseVal || falseVal) << endl;
    cout << "(age < 18) || (salary > 40000): " << ((age < 18) || (salary > 40000)) << endl;

    cout << endl;
    // 逻辑非 (!) - 取反
    cout << "!trueVal: " << (!trueVal) << endl;
    cout << "!falseVal: " << (!falseVal) << endl;
    cout << "!(age >= 18): " << (!(age >= 18)) << endl;

    cout << endl << "=== 复杂逻辑表达式 ===" << endl;
    // 复杂逻辑表达式
    bool isEligible = (age >= 18) && (salary > 30000) && hasLicense;
    cout << "贷款资格：" << isEligible << endl;
    bool canVote = (age >= 18) || (age < 18 && hasLicense); // 注意：这个逻辑不太合理，仅为演示
    cout << "投票资格：" << canVote << endl;
    return 0;
}

运行结果

=== 逻辑运算符示例 ===
trueVal = 1, falseVal = 0
age = 25, salary = 50000, hasLicense = 1
trueVal && falseVal: 0
trueVal && trueVal: 1
(age >= 18) && (hasLicense): 1
trueVal || falseVal: 1
falseVal || falseVal: 0
(age < 18) || (salary > 40000): 1
!trueVal: 0
!falseVal: 1
!(age >= 18): 0
=== 复杂逻辑表达式 ===
贷款资格：1
投票资格：1

4. 赋值运算符

功能

用于给变量赋值。

代码示例

#include <iostream>
using namespace std;

int main() {
    cout << "=== 赋值运算符示例 ===" << endl;
    int a = 10;
    cout << "初始值 a = " << a << endl;

    // 简单赋值
    a = 5;
    cout << "a = 5 后：" << a << endl;

    // 复合赋值运算符
    a += 3; // a = a + 3
    cout << "a += 3 后：" << a << endl;
    a -= 2; // a = a - 2
    cout << "a -= 2 后：" << a << endl;
    a *= 4; // a = a * 4
    cout << "a *= 4 后：" << a << endl;
    a /= 2; // a = a / 2
    cout << "a /= 2 后：" << a << endl;
    a %= 3; // a = a % 3
    cout << "a %= 3 后：" << a << endl;

    cout << endl << "=== 多个变量赋值 ===" << endl;
    // 多个变量赋值
    int x, y, z;
    x = y = z = 100; // 从右向左赋值
    cout << "x = " << x << ", y = " << y << ", z = " << z << endl;

    // 在表达式中使用赋值
    int b = 5;
    int c = (b = 10) + 5; // b 被赋值为 10，然后 c = 10 + 5
    cout << "b = " << b << ", c = " << c << endl;
    return 0;
}

运行结果

=== 赋值运算符示例 ===
初始值 a = 10
a = 5 后：5
a += 3 后：8
a -= 2 后：6
a *= 4 后：24
a /= 2 后：12
a %= 3 后：0
=== 多个变量赋值 ===
x = 100, y = 100, z = 100
b = 10, c = 15

5. 位运算符

功能

对整数在二进制位级别进行操作。

代码示例

#include <iostream>
#include <bitset>
using namespace std;

int main() {
    cout << "=== 位运算符示例 ===" << endl;
    unsigned int a = 5; // 二进制：0101
    unsigned int b = 3; // 二进制：0011
    unsigned int c;

    cout << "a = " << a << " (二进制：" << bitset<4>(a) << ")" << endl;
    cout << "b = " << b << " (二进制：" << bitset<4>(b) << ")" << endl << endl;

    // 按位与 (&) - 两个位都为 1 时结果为 1
    c = a & b;
    cout << "a & b = " << c << " (二进制：" << bitset<4>(c) << ")" << endl;

    // 按位或 (\|) - 至少一个位为 1 时结果为 1
    c = a | b;
    cout << "a | b = " << c << " (二进制：" << bitset<4>(c) << ")" << endl;

    // 按位异或 (^) - 两个位不同时结果为 1
    c = a ^ b;
    cout << "a ^ b = " << c << " (二进制：" << bitset<4>(c) << ")" << endl;

    // 按位取反 (~) - 所有位取反
    c = ~a;
    cout << "~a = " << c << " (二进制：" << bitset<32>(c) << ")" << endl;

    cout << endl << "=== 移位运算符 ===" << endl;
    // 左移 (<<) - 向左移动指定位数，右边补 0
    c = a << 1; // 0101 << 1 = 1010
    cout << "a << 1 = " << c << " (二进制：" << bitset<4>(c) << ")" << endl;
    c = a << 2; // 0101 << 2 = 0100 (假设 4 位表示)
    cout << "a << 2 = " << c << " (二进制：" << bitset<4>(c) << ")" << endl;

    // 右移 (>>) - 向右移动指定位数，左边补 0
    c = a >> 1; // 0101 >> 1 = 0010
    cout << "a >> 1 = " << c << " (二进制：" << bitset<4>(c) << ")" << endl;
    c = a >> 2; // 0101 >> 2 = 0001
    cout << "a >> 2 = " << c << " (二进制：" << bitset<4>(c) << ")" << endl;

    return 0;
}

运行结果

=== 位运算符示例 ===
a = 5 (二进制：0101)
b = 3 (二进制：0011)
a & b = 1 (二进制：0001)
a | b = 7 (二进制：0111)
a ^ b = 6 (二进制：0110)
~a = 4294967290 (二进制：11111111111111111111111111111010)
=== 移位运算符 ===
a << 1 = 10 (二进制：1010)
a << 2 = 20 (二进制：0100)
a >> 1 = 2 (二进制：0010)
a >> 2 = 1 (二进制：0001)

6. 其他运算符

条件运算符（三元运算符）

语法：条件 ? 表达式 1 : 表达式 2

sizeof 运算符

返回类型或对象的大小（字节数）。

逗号运算符

按顺序执行多个表达式，返回最后一个表达式的值。

代码示例

#include <iostream>
using namespace std;

int main() {
    cout << "=== 条件运算符（三元运算符）===" << endl;
    int a = 10, b = 20;
    // 条件运算符：如果条件为真返回第一个值，否则返回第二个值
    int max = (a > b) ? a : b;
    cout << "a = " << a << ", b = " << b << endl;
    cout << "较大值是：" << max << endl;

    // 在输出中使用条件运算符
    cout << "a " << ((a % 2 == 0) ? "是偶数" : "是奇数") << endl;
    cout << "b " << ((b % 2 == 0) ? "是偶数" : "是奇数") << endl;

    cout << endl << "=== sizeof 运算符 ===" << endl;
    // sizeof 运算符
    cout << "sizeof(int): " << sizeof(int) << " 字节" << endl;
    cout << "sizeof(double): " << sizeof(double) << " 字节" << endl;
    cout << "sizeof(char): " << sizeof(char) << " 字节" << endl;
    cout << "sizeof(a): " << sizeof(a) << " 字节" << endl;

    cout << endl << "=== 逗号运算符 ===" << endl;
    // 逗号运算符
    int x, y, z;
    z = (x = 5, y = 10, x + y); // 依次执行 x=5, y=10, 然后返回 x+y
    cout << "x = " << x << ", y = " << y << ", z = " << z << endl;

    // 在 for 循环中使用逗号运算符
    for (int i = 0, j = 10; i < j; i++, j--) {
        cout << "i = " << i << ", j = " << j << endl;
    }
    return 0;
}

运行结果

=== 条件运算符（三元运算符）===
a = 10, b = 20
较大值是：20
a 是偶数
b 是偶数
=== sizeof 运算符 ===
sizeof(int): 4 字节
sizeof(double): 8 字节
sizeof(char): 1 字节
sizeof(a): 4 字节
=== 逗号运算符 ===
x = 5, y = 10, z = 15
i = 0, j = 10
i = 1, j = 9
i = 2, j = 8
i = 3, j = 7
i = 4, j = 6

7. 运算符优先级示例

#include <iostream>
using namespace std;

int main() {
    cout << "=== 运算符优先级示例 ===" << endl;
    int a = 5, b = 3, c = 2;
    int result;

    // 乘法优先级高于加法
    result = a + b * c;
    cout << "a + b * c = " << result << endl; // 5 + (3 * 2) = 11

    // 使用括号改变优先级
    result = (a + b) * c;
    cout << "(a + b) * c = " << result << endl; // (5 + 3) * 2 = 16

    // 关系运算符优先级高于逻辑运算符
    bool logicalResult = a > b && b < c;
    cout << "a > b && b < c = " << logicalResult << endl; // (5 > 3) && (3 < 2) = true && false = false

    // 自增运算符优先级
    int x = 5;
    int y = ++x * 2; // 先自增，再乘法
    cout << "y = ++x * 2: x = " << x << ", y = " << y << endl;

    x = 5;
    y = x++ * 2; // 先乘法，再自增
    cout << "y = x++ * 2: x = " << x << ", y = " << y << endl;

    return 0;
}

运行结果

=== 运算符优先级示例 ===
a + b * c = 11
(a + b) * c = 16
a > b && b < c = 0
y = ++x * 2: x = 6, y = 12
y = x++ * 2: x = 6, y = 10

总结

重要提示：

1. 注意运算符的优先级，不确定时使用括号
2. 自增自减运算符的前置和后置有重要区别
3. 整数除法和浮点数除法结果不同
4. 逻辑运算符有短路求值特性