字符串函数实现

char * stringcpy(char *dest,const char *src){assert((dest!=NULL) && (src!=NULL));char *ret =dest;while((*dest++=*src++)!='/0'){}return ret;}char *stringcat(char *dest,const char *src){assert((dest!=NULL) && (src!=NULL));char *ret=dest;while(*dest!='/0')dest++;while((*dest++=*src++)!='/0'){}return ret;}int stringcmp(const char*s1,const char*s2){assert(s1!=NULL && s2!=NULL);while((*s1==*s2) && *s1){s1++;s2++;}if ((*s1-*s2)>0)return 1;else if((*s1-*s2)<0)return -1;elsereturn 0;}int stringlen(const char * s){assert(s!=NULL);int length=0;while(*s++){length++;}return length;}const char * stringstr(const char *src, const char *sub){assert((src!=NULL)&&(sub!=NULL));const char *p=src;const char *q=sub;while(*p!='/0'){const char *ret =p;while((*p++==*q++) && *q){}if(*q=='/0'){return ret;}else{q=sub;p=++src;}}return NULL;}int stringchr(const char *src, char c){assert(src);const char *p=src;while(*p!='/0'){if(*p==c){return (int)(p-src+1);}p++;}return -1;}const char* stringpbrk(const char *src, const char *sub){const char *p=src;const char *q=sub;while(*q!='/0'){while((*p!=*q)&& *p){p++;}if(*p!='/0')return p;else{q=sub++;p=src;}}return NULL;} char *stringrev(char *src){int length=strlen(src);char *ret =new char[length];for(int i=0;i<length;i++){*(ret+length-i-1)=*(src+i);}return ret;}