TCPL 习题集 第三章

3-2.c

//escape 与 unescape，针对 \n 与 \t 做转义或逆操作。

#include <stdio.h>

void escape(char[], char[]);
void unescape(char[], char[]);
int strlen(char[]);
 
int main() {

    char s[] = "haha\n\tThe\ttime\tis\tcoming!";
    char t[80];
    char t1[80];
    escape(s, t);
    printf("%s\n", t);
    unescape(t, t1);
    printf("%s\n", t1);
}

void escape(char s[], char t[]) {
    int i, j;
    for(i = j = 0; i < strlen(s); j++, i++) {
        switch(s[i]) {
        case '\n' :
            t[j] = '\\';
            t[++j] = 'n';
            break;
        case '\t' :
            t[j] = '\\';
            t[++j] = 't';
            break;
        default:
            t[j] = s[i];
        }
    }
    t[j] = '\0';
}

void unescape(char s[], char t[]) {
    int i, j;
    int preSlash = 0;
    for(i = j = 0; i < strlen(s); j++, i++) {
        switch(s[i]) {
        case '\\' :
            preSlash = 1;
            --j;
            break;
        case 't' :
            if(preSlash) {
                t[j] = '\t';
            } else {
                t[j] = 't';
            }
            preSlash = 0;
            break;
        case 'n' :
            if(preSlash) {
                t[j] = '\n';
            } else {
                t[j] = 'n';
            }
            preSlash = 0;
            break;
        default:
            preSlash = 0;
            t[j] = s[i];
        }
    }
    t[j] = '\0';
}

int strlen(char s[]) {
    int i = 0;
    while(s[i] != '\0')
        ++i;
    return i;
}

3-3.c

/*
 编写函数 expand(s1, s2)，将字符串 s1 中类似于 a-z 一类的速记符号在字符串 s2 中扩展为等价的完整列表 abc...xyz。
 该函数可以处理大小写字母和数字，并可以处理 a-b-c、a-z0-9 与 -a-z 等类似的情况。作为前导和尾随的 - 字符鸳鸯排印。
*/

#include <stdio.h>

void expand(char[], char[]);
int strlen(char[]);
 
int main() {
    char s1[] = "a-a-Z-D";
    char s2[100];
    expand(s1, s2);
    printf("%s\n", s2);
}

void expand(char s1[], char s2[]) {
    int len = strlen(s1);
    int i, j, isValid, isFulfill, isBegin, type = -1; // isValid: 字符是否是字母或数字；isFulfill:
    char c, before, after;

    i = j = isValid = isFulfill = isBegin = 0;
    before = after = '\0';

    while((c = s1[i++]) != '\0') {
        if(c >= 'a' && c <= 'z') {
            if(type != -1) {
                if(type != 0 || c < before) {
                    if(isBegin) {
                        s2[j++] = '-';
                    }
                    isBegin = 0;
                }
            }
            type = 0;
            isValid = 1;
        } else if(c >= '0' && c <= '9') {
            if(type != -1) {
                if(type != 1 || c < before) {
                    if(isBegin) {
                        s2[j++] = '-';
                    }
                    isBegin = 0;
                }
            }
            type = 1;
            isValid = 1;
        } else if(c >= 'A' && c <= 'Z') {
            if(type != -1) {
                if(type != 2 || c < before) {
                    if(isBegin) {
                        s2[j++] = '-';
                    }
                    isBegin = 0;
                }
            }
            type = 2;
            isValid = 1;
        } else {
            isValid = 0;
        }

        if(isValid) {
            if(isBegin) {
                while(++before <= c) {
                    s2[j++] = before;
                }
                isBegin = isFulfill = 0;
                type = -1;
            } else {
                s2[j++] = c;
                isFulfill = 1;
                before = c;
            }
        } else if(c == '-') {
            if(isFulfill) {
                isBegin = 1;
            } else {
                s2[j++] = c;
                isBegin = isFulfill = 0;
                isValid = 0;
            }
        } else {
            s2[j++] = c;
            isValid = isBegin = isFulfill = 0;
            type = -1;
        }
    }
    s2[j] = '\0';
}


int strlen(char s[]) {
    int i = 0;
    while(s[i] != '\0')
        ++i;
    return i;
}

3-5.c

//进制转换
#include <stdio.h>

void itob(int, char[], int);
int strlen(char[]);
void reverse(char[]);
 
int main() {
    char s[80];
    itob(44, s, 2);
    printf("%s\n", s);
}

void itob(int n, char s[], int b) {
    char t[] = "0123456789abcdefghijklmnopqrstuvw";
    int sign = n, i = 0, r;
    if(b <= 1 || b > 32) {
        s[0] = '\0';
        return;
    }
    if(sign < 0) {
        n = -1 * n;
    }

    do {
        s[i++] = t[n % b];
    } while((n /= b) > 0);

    if(sign < 0) {
        s[i++] = '-';
    }
    s[i] = '\0';
    reverse(s);
}


int strlen(char s[]) {
    int i = 0;
    while(s[i] != '\0')
        ++i;
    return i;
}

void reverse(char s[]) {
    char c;
    for(int i = 0, j = strlen(s) - 1; i < j; i++, j--) {
        c = s[i];
        s[i] = s[j];
        s[j] = c;
    }
}