C语言判断

if判断成绩等级

#include <stdio.h>

/* 
  if判断成绩等级:
  输入成绩判断对应的等级
*/
int main(void){

	int grade;
	printf("Please input your grade\n");
	scanf("%d",&grade);	
	
	while (grade > 100 || grade < 0){	
	
		printf("input error,Please input your grade again\n");
		scanf("%d", &grade);
		printf("grade=%d\n",grade);
		/*
		* 0<= grade <= 100
		* 这个比较方式,当出现负值时会出现问题,负数为有符号整形,在进行比较运算时,有符号整形会被隐式转换为无符号整形
		* 例如: 
		* greade = -20; 
		* 0<= -20 <= 100 隐式转换后为 0<= 20 <= 100;
		*/
		if (grade >= 0 && grade <= 100){
			break;
		}
	}
	
	if (grade >= 90){
		printf("A\n");
	}
	else if (90 > grade && grade >= 80){
		printf("B\n");
	}
	else if (80 > grade && grade >= 70){
		printf("C\n");
	}
	else if (70 > grade && grade >= 60){
		printf("D\n");
	}
	else if (grade < 60){
		printf("dream\n");	
	}

	return 0;

}

三个数求最大值

#include <stdio.h>

/*
  三个数求最大值
*/
int main(void) {

	int num1, num2, num3;
	scanf("%d%d%d", &num1, &num2, &num3);

	if ( num1 >= num2 ) {
		if ( num1 >= num3 ) {
			printf("max = %d", num1);
		}
		else if (num1 <= num3) {
			printf("max = %d", num3);
		}
	}
	else if (num1 <= num2 ) {
		if (num2 >= num3) {
			printf("max = %d", num2);
		}
		else if (num2 <= num3) {
			printf("max = %d", num3);
		}
	}

	return 0;
}

#include <stdio.h>

/*
* Maximize the number of three ternary operators 
*/
int main(void) {

	int num1, num2, num3;
	scanf("%d%d%d", &num1, &num2, &num3);

	int num = num1 >= num2 ? num1 >= num3 ? num1 : num3 : num2 >= num3 ? num2 : num3;

	printf("max = %d", num);

	return 0;
}