c语言期末测试

正负相和

//正负项和-------  
void code2_8() {  
    int denominator = 1, flag = 1, i, n;  
    double item = 1, sum = 0;  
    scanf("%d", &n);  
    for (i = 1; i <= n; i++) {  
        sum += item;  
        flag = -flag;  
        denominator += 2;  
        item = flag * 1.0 / denominator;  
    }  
    printf("sum = %f\n", sum);  
}

统计空格or换行,数字,英文个数(switch)

void code3_10_1(){  
    int blank= 0,digit = 0,i,n,other = 0;  
    char ch;  
    scanf("%d",&n);  
    for(i = 0;i < n;i++){  
        ch = getchar();  
        switch(ch){  
            case ' ':  
                blank++;  
                break;  
            case '\n':  
                blank++;  
                break;  
            case '0':  
            case '1':  
            case '2':  
            case '3':  
            case '4':  
            case '5':  
            case '6':  
            case '7':  
            case '8':  
            case '9':  
                digit++;  
                break;  
            default:  
                other++;  
        }  
    }  
    printf("blank = %d, digit = %d, other = %d",blank,digit,other);  
} 

斐波那契数列

void code4_9() {  
    int  n;  
    int fib[46] = {1, 1};  
    scanf("%d", &n);  
    if (n >= 1 && n <= 46) {  
        for (int i = 2; i < n; i++) {//从第三位开始, 滚动前进  
            fib[i] = fib[i - 1] + fib[i - 2];  
        }  
        for (int i = 0; i < n; i++) {  
            printf("%6d", fib[i]);  
            if ((i + 1) % 5 == 0) {  
                printf("\n");  
            }  
        }  
        if (n % 5 != 0) {  
            printf("\n");  
        }  
  
    }else{  
        printf("Invalid.\n");  
    }  
}

阶乘合

double my_fact(int n){  
    int i;  
    double result = 1;  
    if(n<0){  
        return 0;  
    }  
    for(i = 1;i<=n;i++){  
        result*=i;  
    }  
    return result;  
}  
//阶层和------  
void code4_7(){  
    int i,n;  
    double sum = 0;  
    scanf("%d",&n);  
    for(i = 1;i<=n;i++){  
        sum += my_fact(i);  
    }  
    printf("%.0f",sum);  
}

统计区间内素数和

void code4_10(){  
    int m, n;  
    scanf("%d %d", &m, &n);  
    int sum = 0, count = 0;  
    for (int i = m; i <= n; ++i) {  
        int flag = 1;  
        if(i == 1) flag = 0;//1不是素数  
        for (int j = 2; j <= sqrt(i) + 1; ++j) {  
            if (i % j == 0) {//不是素数  
                flag = 0;  
                break;  
            }  
        }  
        if(i == 2) flag = 1;  
        if (flag) {  
            sum += i;  
            count++;  
        }  
    }  
    printf("%d %d", count, sum);  
}

数字金字塔

void pyramid(int n) {  
    for (int i = 1; i <= n; i++) {  
        for (int j = 1; j <= n - i; j++) { 
            printf(" ");  
        }  
        for (int j = 1; j <= i; j++) {  
            printf("%d ", i);  
        }  
        printf("\n");  
    }  
}  
  
//n的数字金字塔  
void code5_6() {  
    int n;  
    scanf("%d", &n);  
    pyramid(n);  
}

调用静态变量的函数计算n!

double fact_s(int n){  
    static double f = 1;//静态变量在程序执行前进行一次初始化  
    f*=n;  
    return f;  
}  
//调用静态变量的函数计算n!  
void code5_9(){  
    int n;  
    scanf("%d",&n);  
    for(int i = 1;i<=n;i++){  
        printf("%3d!=%.0f\n",i,fact_s(i));  
    }  
}

统计单词个数

//统计单词个数  
void code6_5(){  
    int cnt=0,word=0;  
    char ch;  
    while((ch = getchar())!= '\n'){  
        if(ch == ' '){  
            word = 0;  
        } else if(word == 0){  
            word = 1;  
            cnt++;  
        }  
    }  
    printf("%d\n",cnt);  
}

选择排序

//选择排序  
void code7_5() {  
    int arr[] = {21, 4, 1, 6, 7, 1, 45};  
    int n = sizeof(arr) / 4;  
    int min_index;  
    for (int i = 0; i < n - 1; i++) {  
        min_index = i;  
        for (int j = i + 1; j < n; j++) {  
            if(arr[min_index]>arr[j]){  
                min_index = j;  
            }  
        }  
        if(arr[i]!=arr[min_index]){  
            arr[i]^=arr[min_index]^=arr[i]^=arr[min_index];  
        }  
    }  
    for(int i : arr){  
        printf("%d,",i);  
    }  
}

二分查找

//二分查找  
void code7_7() {  
    int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};  
    int n = sizeof(arr) / 4, x;  
    scanf("%d", &x);  
    int low = 0, high = n - 1, mid;  
    while (low <= high) {  
        mid = (low + high) / 2;  
        if (x == arr[mid]) {  
            break;  
        } else if (x < arr[mid]) {  
            high = mid - 1;  
        } else { // x> arr[mid]  
            low = mid + 1;  
        }  
    }  
    if(low <= high){  
        printf("Index is %d\n",mid);  
    } else{  
        printf("Not Found\n");  
    }  
}

方阵转置

//方阵转置  
void code7_9() {  
    int n;  
    scanf("%d", &n);  
    int arr[n][n];  
    for (int i = 0; i < n; i++) {  
        for (int j = 0; j < n; ++j) {  
            arr[i][j] = i * n + j + 1;  
        }  
    }  
    for (int i = 0; i < n; i++) {  
        for (int j = 0; j < n; j++) {  
            if (i <= j) {  
                int temp = arr[i][j];  
                arr[i][j] = arr[j][i];  
                arr[j][i] = temp;  
            }  
        }  
    }  
    for (int i = 0; i < n; i++) {  
        for (int j = 0; j < n; j++) {  
            printf("%4d", arr[i][j]);  
        }  
        printf("\n");  
    }  
  
}

回文

//回文  
void code7_11() {  
    //字符串输入-----------  
    char line[80];  
    int k = 0;  
    while ((line[k] = getchar()) != '\n') {  
        k++;  
    }  
    line[k] = '\0';  
    //判断回文------------  
    int i = 0;  
    k -= 1;  
    while(i<k){  
        if(line[i]!=line[k]){  
            break;  
        }  
        i++;  
        k--;  
    }  
    if(i>=k){  
        printf("It is a palindrome\n");  
    }else{  
        printf("It is not a palindrome\n");  
    }  
}

凯撒密码

//凯撒密码  
void code7_12() {  
    char str[80];  
    int i = 0;  
    while ((str[i] = getchar()) != '\n') {  
        i++;  
    }  
    str[i] = '\0';  
    //输入offset  
    int offset;  
    scanf("%d", &offset);  
    if (offset >= 26) {  
        offset %= 26;  
    }  
    for (i = 0; str[i] != '\0'; i++) {  
        if (str[i] >= 'A' && str[i] <= 'Z') {  
            if ((str[i] - 'A' + offset) < 26) {  
                str[i] += offset;  
            } else {  
                str[i] -= 26 - offset;  
            }  
        } else if (str[i] >= 'a' && str[i] <= 'z') {  
            if ((str[i] - 'a' + offset) < 26) {  
                str[i] += offset;  
            } else {  
                str[i] -= 26 - offset;  
            }  
        }  
    }  
    for (i = 0; str[i] != '\0'; i++) {  
        putchar(str[i]);  
    }  
    printf("\n");  
}

输入年份和天数, 输入年月日

void month_day(int year, int year_day, int *pmonth, int *pday) {  
    int tab[2][13] = {  
            {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},  
            {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},  
    };  
    int is_leap = (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;  
    int k = 1;  
    for (; year_day > tab[is_leap][k]; k++) {  
        year_day -= tab[is_leap][k];  
    }  
    *pmonth = k;  
    *pday = year_day;  
}

冒泡排序

//冒泡法  
void code8_5() {  
    int arr[] = {7, 4, 7, 3, 22, 72, 2};  
    int n = sizeof(arr) / 4;  
    for (int i = 0; i < n - 1; i++) {  
        for (int j = 0; j < n - i - 1; j++) {  
            if (arr[j] > arr[j + 1]) {  
                arr[j] ^= arr[j + 1] ^= arr[j] ^= arr[j + 1];  
            }  
        }  
    }  
    for (int i = 0; i < n; i++) {  
        printf("%d, ",arr[i]);  
    }  
}

指针计算元素个数

//指针计算元素个数及存储元素  
void code8_7() {  
    double a[2], *p, *q;  
    p = &a[0];  //指针p指向数组a的首地址  
    q = p + 1;    //指针q指向数组元素a[1]  
    printf("%d\n", q - p); //计算指针p和q之间的元素的个数  
    printf("%d\n", (int)q - (int)p);//计算指针p和q之间的字节数\  
}

字符压缩

void zip(char *p) {  
    char *q = p;  
    int n;  
    while (*p != '\0') {  
        n = 1;  
        while (*p == *(p + n)) {  
            n++;  
        }  
        if (n >= 10) {  
            *q++ = (n / 10) + '0';  
            *q++ = (n % 10) + '0';  
        } else if (n >= 2) {  
            *q++ = n + '0';  
        }  
        *q++ = *(p + n - 1);  
        p += n;  
    }  
    *q = '\0';  
}

最小串

//最小串  
void code8_9() {  
    int n;  
    char sx[80], smin[80];  
    scanf("%d", &n);  
    scanf("%s", sx);  
    strcpy(smin, sx);  
    for (int i = 1; i < n; i++) {  
        scanf("%s",sx);  
        if(strcmp(sx,smin)<0){//找到最小串  
            strcpy(smin,sx);  
        }  
    }  
    printf("min is %s \n",smin);  
}

递归求最大公约数

int gcd(int m, int n) {  
    if (m % n == 0) {  
        return n;  
    } else {  
        return gcd(n, m % n);  
    }  
}  
//递归求最大公约数  
void code10_3() {  
    int n, m;  
    scanf("%d %d", &m, &n);  
    printf("%d", gcd(m, n));  
}

递归求n!

int fact(int n){  
    if(n==1||n ==0){  
        return 1;  
    }  
    return n* fact(n-1);  
}  
//递归求n!  
void code10_2(){  
    int n;  
    scanf("%d",&n);  
    printf("%d",fact(n));  
}

带参宏定义

#define MAX(a, b) a>b?a:b  
#define SQR(x) x*x  
//带参数的宏定义  
void code10_8() {  
    int x, y;  
    scanf("%d %d", &x, &y);  
    x = MAX(x,y);  
    y = SQR(x);  
    printf("%d %d\n",x,y);  
}  
#undef MAX  
#undef SQR

指针数组开头字母找单词

//指针数组开头字母找单词  
void code11_1() {  
    char ch;  
    const char *color[5] = {"red", "blue", "yellow", "green", "black"};  
    ch = getchar();  
    int flag = 0;  
    for (int i = 0; i < 5; ++i) {  
        if (*color[i] == ch) {  
            flag = 1;  
            puts(color[i]);  
        }  
    }  
    if(flag == 0){  
        printf("Not Found\n");  
    }  
}

串从小到大用指针排序

void fsort(const char *color[], int n) {  
    const char *temp;  
    for (int k = 0; k < n-1; k++) {//冒泡排序  
        for (int j = 0; j < n - k -1; j++) {  
            if (strcmp(color[j], color[j + 1]) > 0) {  
                temp = color[j];  
                color[j] = color[j+1];  
                color[j+1] = temp;  
            }  
        }  
    }  
}  
//5个串从小到大用指针排序  
void code11_4() {  
    const char *pcolor[5] = {"red", "blue", "yellow", "green", "black"};  
    fsort(pcolor, 5);  
    for (int i = 0; i < 5; i++)printf("%s ", pcolor[i]);  
}

藏头诗

//藏头诗  
void code11_5() {  
    int i, n = 0;  
    char *poem[20], str[80], mean[20];  
    gets(str);  
    while (str[0] != '#') {  
        poem[n] = (char *) malloc(sizeof(char) * (strlen(str) + 1));  
        strcpy(poem[n], str);  
        n++;  
        gets(str);  
    }  
    for (i = 0; i < n; i++) {  
        mean[i] = *poem[i];  
        free(poem[i]);  
    }  
    mean[i] = '\0';  
    puts(mean);  
}