题解 | #单词替换#

#include<iostream>
#include<string>

using namespace std;

void Question4_2(){//习题4.2  北京大学  单词替换 
	
	string words,search,replace;
	int rep = replace.size();
	while(getline(cin,words)){
		cin>>search>>replace;
		int i=0,j=0;
		while(i<=words.size()){
			while(words[j]!=' '&&words[j]!='\0') j++;//i是首字母 j是后空格
			string current = words.substr(i,j-i);//空格去掉，不+1 
			if(current==search){
				string a = words.substr(0,i);
				string b = words.substr(j);//默认npos 
                
				words = a+replace+b;
				j =  a.size()+rep;//进入后空格
			}
			i = ++j;//跳过后空格
		}
		cout<<words<<endl;
	}
}

int main(){
    Question4_2();
    return 0;
}