CareerCup1.4

Question1.4:

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. (Note: if implementing in
Java, please use a character array so you can perform this operation in place.) EXAMPLE Input : "Mr John Smith " Output: "Mr%20John%20Smith"

先算出替换空格后string的结束位置，再从此结束位置开始由后向前的进行再填充，中途遇到空格则依次填充'0''2''%'

代码：

#include "stdafx.h"
#include <string>
#include <iostream>
 
void ReplaceSpace(std::string&);
int main()
{
  using namespace std;
  string str;
	getline(cin,str);
	//Find the number of ' ' and the end of meaningful chars
	ReplaceSpace(str);
	cout<<str<<endl;
	return 0;
}
 
void ReplaceSpace(std::string& str)
{
	int numofSpace=0;
	int endofchars=-1;
	bool meaningfulchar=false;
	for(int i=str.size()-1;i>=0;i--)
	{
 
		if(meaningfulchar&&str[i]==' ')
		{
			numofSpace++;
		}
		if(meaningfulchar==false&&str[i]!=' ')
		{
			endofchars = i;
			meaningfulchar = true;
		}
	}
	int currentPos=endofchars+2*numofSpace;
	for(int i=endofchars;i>=0;i--)
	{
		if(str[i]!=' ')
		{
			str[currentPos] = str[i];
			currentPos--;
		}
		else
		{
			str[currentPos]='0';
			str[currentPos-1]='2';
			str[currentPos-2]='%';
			currentPos-=3;
		}
	}
}