C and pointer (pointers on C) -- Chapter 4: Answers to the exercises of the statements (below)

Please see http://download.csdn.net/download/wangpegasus/5701765

In chapter 4

1,

#include "stdafx.h"double sqrt(double temp){double before, after;before = 1.0;after = 1.0;do{before = after;after = (before + temp/before)/2;} while (before != after);return after;}int _tmain(int argc, _TCHAR* argv[]){double temp,result;puts("input N:");scanf_s("%lf",&temp);result = sqrt(temp);printf("sqrt N = %lf \n",result);return 0;}

2,

#include "stdafx.h"int _tmain(int argc, _TCHAR* argv[]){int length = 100;puts("Prime(1~100):\n");for (int i = 1; i <= length; i++){int ALU = 0;for (int j =1; j <= i; j++){if (i%j == 0){ALU++;}}if (ALU == 2){printf("%d\t", i);}}return 0;}

3,

# Include "stdafx. H "int _ tmain (INT argc, _ tchar * argv []) {int A, B, C; puts (" input three-sided length (A, B, C ): \ n "); do {scanf_s (" % d, % d, % d ", & A, & B, & C) ;}while (A + B) <= c | (A + C) <= B | (B + C) <= A); If (A = B) & (B = C) {puts ("equals edge! ");} Else if (A = B) | (B = C) | (C = A) {puts ("! ");} Else {puts (" not equal! ");} Return 0 ;}

4. 2b method:

void copy_n( char dst[], char src[], int n ){int i,l_src;l_src = 0;for (i = 0; dst[i] == '\0'; i++){l_src++;}if (l_src < n){for (i = 0; i < l_src; i++){dst[i] = src[i];}for (i = l_src; i < n; i++){dst[i] = '\0';}}else{for (i = 0; i < n; i++){dst[i] = src[i];}}}

Correct practice:

void copy_n( char dst[], char src[], int n ){int dst_index, src_index;src_index = 0;for (dst_index = 0; dst_index < n; dst_index++){dst[dst_index] = src[src_index];if (src[src_index] != 0){src_index++;}}}

5. Too many strings are involved, slightly.
6,

void substr(char dst[], char src[], int start, int len){int dst_index, src_index, l_src;l_src =src_index = 0;do{l_src++;} while (src[l_src] != '\0' );if (start < 0 || len < 0 || start > l_src ++){dst[0] = '\0';}else{for ( dst_index = 0; dst_index < len; dst_index++){dst[dst_index] = src[src_index + start];if (src[src_index] != '\0'){src_index++;}}}}

7,

void deblank(char string[]){char copy_str[] = {'\0'};int str_index, copy_str_index, temp = 0;for ( str_index = 0; string[str_index] != '\0'; str_index++){if (string[str_index] == ' '){if (temp > 0){continue;}else{copy_str_index++;copy_str[copy_str_index] = string[str_index];temp++;}}else{copy_str_index++;copy_str[copy_str_index] = string[str_index];}}copy_str[copy_str_index++] = '\0';for ( copy_str_index = 0; copy_str[copy_str_index] != '\0'; copy_str_index++){string[copy_str_index]= copy_str[copy_str_index];}string[copy_str_index + 1] = '\0';}