七、判断

1、if语句

#include <stdio.h>
 
int main()
{
    int x;
    scanf("%d", &x);
    int f=0;
    if ( x < 0 ) {
        f = -1;
    } else if ( x == 0 ) {
        f = 0;
    } else if ( x >5 ) {
        f = 2 * x;
    } else {
        f = 3*x;
    }
 
    printf("%d\n", f);
 
    return 0;
}

2、switch..case语句

#include <stdio.h>
 
int main()
{
    printf("输入成绩（0-100）");
    int grade;
    scanf("%d", &grade);
    grade /=10;
    switch ( grade ) {
    case 10:
    case 9:
        printf("A\n");
        break;
    case 8:
        printf("B\n");
        break;
    case 7:
        printf("C\n");
        break;
    case 6:
        printf("D\n");
        break;
    default:
        printf("F\n");
        break;
    }
 
    return 0;
}

#include <stdio.h>
 
int main()
{
 
    printf("请输入月份：");
    int month;
    scanf("%d", &month);
 
    switch ( month )
    {
 
        case 1: printf("January\n"); break;
        case 2: printf("February\n"); break;
        case 3: printf("March\n"); break;
        case 4: printf("April\n"); break;
        case 5: printf("May\n"); break;
        case 6: printf("June\n"); break;
        case 7: printf("July\n"); break;
        case 8: printf("August\n"); break;
        case 9: printf("September\n"); break;
        case 10:printf("October\n"); break;
        case 11:printf("November\n"); break;
        case 12:printf("December\n"); break;
    }
 
    return 0;
}