例题第7章

7.1

#include<stdio.h>
int main(void)
{
    int count[9];
    int i,response;

    for(i=1;i<=8;i++)
        count[i]=0;
    for(i=1;i<=10;i++){
        printf("input your response:");
        scanf("%d",&response);
        if(response < 1||response>8)
            printf("this is a bad response:%d\n",response);
        else
            count[response]++;
    }

    printf("result:\n");
    for(i=1;i<=8;i++)
        printf("%4d%4d\n",i,count[i]);

    return 0;
}

7.2

#include<stdio.h>
int main(void)
{
    int i;
    int fib[10]={1,1};

    for(i=2;i<10;i++)
        fib[i]=fib[i-1]+fib[i-2];

    for(i=0;i<10;i++){
        printf("%6d",fib[i]);
        if((i+1)%5 == 0)
            printf("\n");
    }

    return 0;
}

7.3

#include<stdio.h>
int main(void)
{
    int i,flag,x;
    int a[5];

    printf("Enter 5 integers:");
    for(i=0;i<5;i++)
        scanf("%d",&a[i]);
    printf("Enter x");
    scanf("%d",&x);
    flag=0;
    for(i=0;i<5;i++)
        if(a[i]==x){
            printf("Index is %d\n",i);
            flag=1;
            break;
        }
        if(flag == 0)
            printf("Not Found\n");

        return 0;
}

7.4

#include<stdio.h>
int main(void)
{
    int i,index,n;
    int a[10];

    printf("Enter n:");
    scanf("%d",&n);
    printf("Enter %d integers:",n);
    for(i=0;i<n;i++)
        scanf("%d",&a[i]);
    index=0;
    for(i=1;i<n;i++)
        if(a[i]<a[index])
            index=i;
        printf("min is %d\tsub is %d\n",a[index],index);

        return 0;
}

7.5

#include<stdio.h>
int main(void)
{
    int i,index,k,n,temp;
    int a[10];

    printf("Enter n:");
    scanf("%d",&n);
    printf("Enter %d integers:",n);
    for(i=0;i<n;i++)
        scanf("%d",&a[i]);
    for(k=0;k<n-1;k++){
        index=k;
        for(i=k+1;i<n;i++)
            if(a[i]<a[index]) index=i;
            temp=a[index];
            a[index]=a[k];
            a[k]=temp;
    }
    printf("After sorted:");
    for(i=0;i<n;i++)
        printf("%d",a[i]);

    return 0;
}

7.6

#include<stdio.h>
int main(void)
{
    int a[10]={1,2,3,4,5,6,7,8,9,10};
    int low ,high,mid,n=10,x;

    printf("Enter x: ");
    scanf("%d",&x);

    low=0;high=n-1;
    while(low<=high) {
        mid=(low+high)/2;
        if(x == a[mid])
            break;
        else if(x<a[mid])
            high=mid-1;
        else
            low=mid+1;
        }
        if(low<=high)
            printf("Index is %d\n",mid);
        else
            printf("Not Found\n");

        return 0;

    }

7.7

#include<stdio.h>
int main(void)
{
    int col,i,j,row;
    int a[3][2];

    printf("Enter 6 integers:\n");
    for(i=0;i<3;i++)
        for(j=0;j<2;j++)
            scanf("%d",&a[i][j]);

        for(i=0;i<3;i++){
            for(j=0;j<2;j++)
                printf("%4d",a[i][j]);
            printf("\n");
        }

        row=col=0;
        for(i=0;i<3;i++)
            for(j=0;j<2;j++)
                if(a[i][j]>a[row][col]){
                    row=i;
                    col=j;
                }
                printf("max = a[%d][%d]=%d\n",row,col,a[row][col]);

                return 0;
}

7.8

#include<stdio.h>
int main(void)
{
    int i,j;
    int a[3][2];

    for(i=0;i<3;i++)
        for(j=0;j<2;j++)
            a[i][j]=i+j;

        for(i=0;i<3;i++){
            for(j=0;j<2;j++)
                printf("%4d",a[i][j]);
            printf("\n");
        }
        return 0;
}

7.9

#include<stdio.h>
int main(void)
{
    int i,j,n,temp;
    int a[6][6];
    
    printf("Enter n:");
    scanf("%d",&n);
    for(i=0;i<n;i++)
        for(j=0;j<n;j++)
            a[i][j]=i*n+j+1;

        for(i=0;i<n;i++)
            for(j=0;j<n;j++)
                if(i<=j){
                    temp=a[i][j];
                    a[i][j]=a[j][i];
                    a[j][i]=temp;
                }

                for(i=0;i<n;i++){
                    for(j=0;j<n;j++)
                        printf("%4d",a[i][j]);
                    printf("\n");
                }

                return 0;
}

7.11

#include<stdio.h>
int main(void)
{
    int i,j,n,temp;
    int a[6][6];
    
    printf("Enter n:");
    scanf("%d",&n);
    for(i=0;i<n;i++)
        for(j=0;j<n;j++)
            a[i][j]=i*n+j+1;

        for(i=0;i<n;i++)
            for(j=0;j<n;j++)
                if(i<=j){
                    temp=a[i][j];
                    a[i][j]=a[j][i];
                    a[j][i]=temp;
                }

                for(i=0;i<n;i++){
                    for(j=0;j<n;j++)
                        printf("%4d",a[i][j]);
                    printf("\n");
                }

                return 0;
}

7.12

#include<stdio.h>
int main(void)
{
    int i,number;
    char str[10];

    printf("Enter a string:");
    i=0;
    while((str[i]=getchar())!='\n')
        i++;
    str[i]='\0';

    number=0;
    for(i=0;str[i]!='\0';i++)
        if(str[i]>='0'&&  str[i]<='9')
            number=number*10+str[i]-'0';

        printf("digit=%d\n",number);

        return 0;
}

7.13

#include<stdio.h>
int main(void)
{
    int count,i;
    char str[80];

    printf("Enter a string:");
    i=0;
    while((str[i]=getchar())!='\n')
        i++;
    str[i]='\0';

    count=0;
    for(i=0;str[i]!='\0';i++)
        if(str[i]<='9'&&str[i]>='0')
            count++;
        printf("count=%d\n",count);

        return 0;
}

7.14

#include<stdio.h>
int main(void)
{
    int i,k;
    char str1[80],str2[80];
    long number;
    printf("Enter a string:");
    i=0;
    while((str1[i]=getchar())!='\n')
        i++;
    str1[i]='\0';

    k=0;
    for(i=0;str1[i]!='\0';i++)
        if
            (str1[i]>='0'&&str1[i]<='9'||str1[i]>='a'&&str1[i]<='f'||str1[i]>='A'&&str1[i]<='F')
        {
            str2[k]=str1[i];
            k++;
        }
        str2[k]='\0';

        number=0;
        for(i=0;str2[i]!='\0';i++)
            if(str2[i]>='0'&&str2[i]<='9')
                number=number*16+str2[i]-'0';
            else if(str2[i]>='a'&&str2[i]<='f')
                number=number*16+str2[i]-'a'+10;
            else if(str2[i]>='A'&&str2[i]<='F')
                number=number*16+str2[i]-'A'+10;

            printf("New string:");
            for(i=0;str2[i]!='\0';i++)
                putchar(str2[i]);
            printf("\n");
            printf("number=%ld\n",number);

            return 0;
}