How to write if in c language to judge multiple conditions

In C language, if statement is usually used to execute a specific block of code based on a single condition. However, multiple conditions can be combined to make a determination using logical operators such as &&, ||, and !. Including using logical AND (&&) to judge multiple conditions, using logical OR (||) to judge at least one condition, using logical NOT (!) to judge the negation of a single condition, as well as nesting if statements and using parentheses to clarify priority.

In C language, if statement is usually used to execute a specific block of code based on a single condition. However, if you want to execute code based on multiple conditions, you can use logical operators such as &&, ||, and ! to combine the conditions.

The following are some examples showing how to use if statements to determine multiple conditions in C language:

1. Use logical AND ( &&) Judge multiple conditions

When you want to check whether all conditions are true, you can use the logical AND operator &&.

c

##

#include <stdio.h>  
  
int main() {  
    int a = 5;  
    int b = 10;  
  
    if (a > 0 && b > 0) {  
        printf("a 和 b 都大于 0\n");  
    } else {  
        printf("至少有一个数不大于 0\n");  
    }  
  
    return 0;  
}

2. Use logical OR (||) to determine multiple conditions

When you want to check that at least one condition is true, you can use the logical OR operator ||.

c

#include <stdio.h>  
  
int main() {  
    int a = -5;  
    int b = 10;  
  
    if (a > 0 || b > 0) {  
        printf("至少有一个数大于 0\n");  
    } else {  
        printf("两个数都不大于 0\n");  
    }  
  
    return 0;  
}

3. Use logical NOT (!) to determine the negation of a single condition

If you want to check if a condition is not true, you can use the logical NOT operator!.

c

#include <stdio.h>  
  
int main() {  
    int a = 0;  
  
    if (!a) {  
        printf("a 不等于 0\n"); // 实际上这里会打印，因为 a 等于 0，所以 !a 为真  
    } else {  
        printf("a 等于 0\n");  
    }  
  
    return 0;  
}

4. Nested if statements

For more complex conditional judgments, you can also use nested if statements.

c

##

#include <stdio.h>  
  
int main() {  
    int a = 5;  
    int b = 10;  
  
    if (a > 0) {  
        if (b > 0) {  
            printf("a 和 b 都大于 0\n");  
        } else {  
            printf("a 大于 0，但 b 不大于 0\n");  
        }  
    } else {  
        printf("a 不大于 0\n");  
    }  
  
    return 0;  
}

5. Use parentheses to clarify priority

When combining multiple logical operators, use parentheses to clearly specify the priority of the operation and avoid confusion.

c

#include <stdio.h>  
  
int main() {  
    int x = 1;  
    int y = 2;  
    int z = 3;  
  
    if ((x == 1 && y == 2) || z == 3) {  
        printf("条件为真\n"); // 这里会打印，因为 (x == 1 && y == 2) 为真，或者 z == 3 也为真  
    } else {  
        printf("条件为假\n");  
    }  
  
    return 0;  
}

When writing an if statement that contains multiple conditions, make sure you The logic is clear and parentheses are used to make your intentions clear. This avoids potential logic errors and makes the code easier to understand and maintain.

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