CC150 1.4

1_4.cpp

/* CC150 1.4
 * Write a method to replace all spaces in a string with'%20'.
 * You may assume that the string has sufficient space at the end of the string to hold the additional characters,
 * and that you are given the "true" length of the string.
 */

#include <iostream>
#include <cstring>

using namespace std;

void replace(char *str) {
	int spaceCount = 0;
	for (char *begin = str, *end = begin + strlen(str);
		begin != end; ++begin) {
		if (*begin == ' ') // count the number of spaces
			++spaceCount;
	}
	//cout << spaceCount << endl;
	size_t newLength = strlen(str) + 2 * spaceCount; // length of replaced string
	//cout << newLength << endl;
	*(str + newLength) = '\0'; // null terminates the new string, assume sufficient space
	char *oldStr = str + strlen(str), *newStr = str + newLength; // point at null character
	while (oldStr != newStr) { // always point one past the current character, would never go past the begining
		if (*(--oldStr) != ' ') // direct copy if not space
			*(--newStr) = *oldStr;
		else { // replace with %20 if hits space
			*(--newStr) = '0';
			*(--newStr) = '2';
			*(--newStr) = '%';
		}
	}
	return;
}

int main()
{
	char s1[50] = " Hello World! "; // normal string with leading and tailing spaces
	char s2[10] = "   "; // string with all spaces
	printf("%s\n", s1);
	printf("%s\n", s2);
	//cout << strlen(s1) << endl;
	replace(s1);
	printf("%s\n", s1);
	replace(s2);
	printf("%s\n", s2);
	return 0;
}