《C语言程序设计（第二版新版）》第二章习题解答（部分）

2-3

//十六进制字符串转化为整型数#include <stdio.h>#define MAXLINE 100void htoi(char s[]);int getline(char line[], int lim);int main(){char s[MAXLINE];while (getline(s, MAXLINE) > 0){printf("origin:%s", s);htoi(s);}}int getline(char line[], int lim){int i, c;i = 0;printf("input:\n");while (i < lim - 1 && (c = getchar()) != '\n' && c != EOF){line[i] = c;i++;}if (c == '\n'){line[i] = c;i++;}line[i] = '\0';return i;}void htoi(char s[])//不支持负数{int i = 0;int n = 0;while (s[i] != '\0'){if (s[i++] != '0');else if (s[i] == 'x' || s[i] == 'X')//确保为16进制数前缀{i++;while ((s[i] >= '0' && s[i] <= '9') || (s[i] >= 'a' && s[i] <= 'f') || (s[i] >= 'A' && s[i] <= 'F'))//确保为16进制数{if (s[i] >= '0' && s[i] <= '9')n = s[i] - '0' + n * 16;else if (s[i] >= 'a' && s[i] <= 'f')n = s[i] - 'a' + 10 + n * 16;elsen = s[i] - 'A' + 10 + n * 16;i++;}if (n != 0)printf("%d\n", n);n = 0;}}}

2-4

/*2-4.Write an alternate version of squeeze(s1,s2) that deletes each character in the string s1that matches any character in the string s2 .*/#include <stdio.h>#define MAXLINE 100void squeeze(char s1[], char s2[]);int getline(char line[], int lim);int main(){char s1[MAXLINE], s2[MAXLINE];getline(s1, MAXLINE);3printf("s1:%ss2:%s\n", s1, s2);squeeze(s1, s2);printf("final:\n%s\n", s1);return 0;}int getline(char line[], int lim){int i, c;i = 0;printf("input:\n");while (i < lim - 1 && (c = getchar()) != '\n' && c != EOF){line[i] = c;i++;}if (c == '\n'){line[i] = c;i++;}line[i] = '\0';return i;}void squeeze(char s1[], char s2[]){int i1, i2, j;char temp; i2 = 0;while ((temp = s2[i2]) != '\0'){i1 = 0;j = 0;for (; s1[j] != '\0'; j++){if (s1[j] != temp)s1[i1++] = s1[j];}s1[i1] = '\0';i2++;}}

2-5

#include <stdio.h>#define MAXLINE 100void any(char s1[], char s2[]);int getline(char line[], int lim);int main(){char s1[MAXLINE], s2[MAXLINE];getline(s1, MAXLINE);getline(s2, MAXLINE);printf("s1:%ss2:%s", s1, s2);any(s1, s2);return 0;}int getline(char line[], int lim){int i, c;i = 0;printf("input:\n");while (i < lim - 1 && (c = getchar()) != '\n' && c != EOF){line[i] = c;i++;}if (c == '\n'){line[i] = c;i++;}line[i] = '\0';return i;}void any(char s1[], char s2[]){int i2, j;char temp; i2 = 0;while ((temp = s2[i2]) != '\0'){j = 0;for (; s1[j] != '\0' && s1[j] != temp; j++) //get j;;if (s1[j] == '\0')printf("%c:%d\n", temp, -1);else{if (s1[j] == '\n')printf("\\n:%d\n", j);elseprintf("%c:%d\n", temp, j);}i2++;}}

2-6

#include <stdio.h>unsigned int setbits(unsigned int, int, int, unsigned int);int main(){unsigned int x, y,answer;int p, n;while (1){printf("x:");scanf("%o", &x);printf("y:");scanf("%o", &y);printf("p:");scanf("%d", &p);printf("d:");scanf("%d", &n);answer = setbits(x, p, n, y);printf("answer=%o\n", answer);}return 0;}unsigned int setbits(unsigned int x, int p, int n, unsigned int y){unsigned temp101, temp010, tempx, tempy;temp010 = (~(~0 << n)) << (p - n + 1);temp101 = ~temp010;tempy = (y << (p - n + 1)) & temp010;tempx = x & temp101;return tempx + tempy;}

2-7

#include <stdio.h>unsigned int invert(unsigned int, int, int);int main(){unsigned int x, answer;int p, n;while (1){printf("x:");scanf("%o", &x);printf("p:");scanf("%d", &p);printf("n:");scanf("%d", &n);answer = invert(x, p, n);printf("answer=%o\n", answer);}return 0;}unsigned int invert(unsigned int x, int p, int n){unsigned temp101, temp010;temp010 = (~(~0 << n)) << (p - n + 1);//printf("temp010:%o\n", temp010);temp101 = ~temp010;//printf("temp101:%o\n", temp101);//printf("x & temp101:%o\n", x & temp101);//printf("(~(x & temp010)) & temp010:%o\n", (~(x & temp010)) & temp010);return x & temp101 + (~(x & temp010) & temp010);}

2-8

#include <stdio.h>unsigned rightrot(unsigned, int);int main(){unsigned int x, answer;int n;while (1){printf("x:");scanf("%o", &x);printf("n:");scanf("%d", &n);answer = rightrot(x, n);printf("answer=%o\n", answer);}return 0;}unsigned rightrot(unsigned int x, int n){unsigned temp, xmove, xadd;int i;xmove = x >> n;printf("xmove:%o\n", xmove);temp = xmove;for (i = 1; temp >= 2; i++)temp /= 2;printf("i:%d\n", i);xadd = (x & ~(~0 << n)) << i;printf("xadd:%o\n", xadd);return xmove + xadd;}

2-9

#include <stdio.h>#define MAXLINE 100int bitsearch(int, int v[], int);void buildarray(int v[],int n);int main(){int x, location, numbers[MAXLINE];x = 0;buildarray(numbers, MAXLINE);while (x != MAXLINE){location = bitsearch(x, numbers, MAXLINE);printf("location is %d\n", location);x++;}return 0;}void buildarray(int v[], int n){int i;for (i = 0; i < n; i++)v[i] = i;}int bitsearch(int x, int v[], int n){int low, mid, high;low = 0;high = n - 1;/**/while (low <= high){mid = (low + high) / 2;  if (x < v[mid])high = mid - 1;else if (x > v[mid])low = mid + 1;elsereturn mid;}return -1;/*/mid = (low + high) / 2;while ((low <= high) && (x != mid)){if (x < v[mid])high = mid - 1;elselow = mid + 1;mid = (low + high) / 2;}if (x == mid)return mid;elsereturn 0;/**/}

2-10

#include <stdio.h>int lower(int);int main(){int c, c_lower;while ((c = getchar()) != '\n'){c_lower=lower(c);printf("result:%c,%d\n", c_lower, c_lower);}return 0;}int lower(int c){return (c >= 'A' && c <= 'Z') ? (c - 'A' + 'a') : c;}