strcat

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#include<iostream>using namespace std;char* stringcatQ(char* b1,char* b2){int length1,length2;length1=strlen(b1);length2=strlen(b2);char* c=new char[length1+length2+1];for(int i=0;i<length1;i++){c[i]=b1[i];}int n=0;for(int k=length1;k<length1+length2;k++){c[k]=b2[n];n++;}    c[length1+length2]='\0';return c;}int main(){char a1[80]="jape";char a2[20]="dogcat";    char* newchar=stringcatQ(a1,a2);cout<<newchar<<endl;delete newchar;return 0;}//有错误 ，只考虑到返回值了，没考虑形参和实参。。

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对上面程序的改进，不过很难看懂啊 ，我自己都迷糊了。#include<iostream>using namespace std;char* stringcatQ(char* b1,char* b2){int length1,length2;length1=strlen(b1);length2=strlen(b2);char* c=new char[length1+length2+1];for(int i=0;i<length1;i++){b1[i]=c[i]=b1[i];}int n=0;for(int k=length1;k<length1+length2;k++){b1[k]=c[k]=b2[n];n++;}    c[length1+length2]='\0';b1[length1+length2]='\0';return c;}int main(){char a1[80]="jape";cout<<a1<<endl;char a2[20]="dogcat";    char* newchar=stringcatQ(a1,a2);cout<<newchar<<endl;cout<<a1;delete newchar;return 0;}

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继续改进

#include<iostream>using namespace std;char* stringcatQ(char* b1,char* b2){int length1,length2;length1=strlen(b1);length2=strlen(b2);int n=0;for(int k=length1;k<length1+length2;k++){b1[k]=b2[n];n++;}    b1[length1+length2]='\0';return b1;}int main(){char a1[80]="jape";cout<<a1<<endl;char a2[20]="dogcat";    char* newchar=stringcatQ(a1,a2);cout<<newchar<<endl;cout<<a1<<endl;return 0;}

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原型

#include<iostream>using namespace std;char* cat(char* dest,const char* sour){char *returnchar=dest;while(*dest){dest++;}while(*dest=*sour)//还可以写成*dest++=*sout++,循环体内为空{dest++;sour++;}cout<<&dest<<" "<<endl;return returnchar;}int main(){char a[100]="how do ";char b[]="you do";char* f=cat(a,b);cout<<f<<endl;return 0; }