洛谷学习总集2
洛谷代码学习总集 2
目录索引
- P1067 输出多项式的字符串
- P1098 将切片展开成完整字符串
P1067 输出多项式的字符串
思路：多项式由：系数，"x"，""指数，组成。其中各项多项式间由"+"连接，如果系数/指数为1则不需要打印系数/""指数。特殊情况：读入1、末两项（指数为1和指数为0）针对特殊情况特殊处理.
坑：
- 拼接字符串并不好玩（ 除非使用sstream 😄 )
- 首项前面不需要加号，末项后面不能有加号，至少需要特殊处理一个（或者在循环内做项数条件判断）
- 0的时候可以直接跳过当前项
代码
#include<iostream>
using std::cin,std::cout;
std::string makeMonomial(const int base,const int pow){
std::string Monomial{};
if(base==1)
Monomial+="";
else if(base==-1)
Monomial+="-";
else
Monomial+=std::to_string(base);
Monomial+="x";
if(pow > 1){
Monomial+="^";
Monomial+=std::to_string(pow);
}
if(base==0) return "";
else if(pow ==0) return std::to_string(base);
else return Monomial;
}
std::string makePolynomial(const int counts){
std::string Polynomial{};
int base;
cin>>base;
Polynomial+=makeMonomial(base,counts);
for (int i = counts-1; i >= 0 ; i--)
{
cin>>base;
if(base>0) Polynomial+='+';
Polynomial+=makeMonomial(base,i);
}
return Polynomial;
}
int main(){
int n;
cin>>n;
cout<<makePolynomial(n);
}
P1098 将切片展开成完整字符串
思路：检测"-",然后看前后字符是否满足要求。按照ASCII码自增/自减填充的字符就可以按顺序输出序列（再加一个内循环就可以重复输出，条件判断来确定是输出ASCII字符还是只输出"*"）。
坑：
- 注意溢出
- 使用迭代器如果搭配replace方法注意小心地址越界，replace是深拷贝，会导致内存地址变化，迭代器在replace后就不能正常工作了！
- 可以构建一个字符串，这样可以实现动态变化，但是也可以实时输出，会更快占用更少的内存
奇怪的注意点： - 字符串对象实质是类，[构建一个字符串]/[传递字符串参数]的速度略低，所以尽可能少构建字符串类对象可以优化一些速度
- 可以使用 std::string& 也就是引用，类似指针，你对传参过来的字符串操作会影响原字符串（注意安全！）
- 如果你喜欢cpp17，其更新了一个std::string_view对象，对于只读场景有更好的性能（具体可以自行了解:D ）
构建串串
#include<iostream>
using std::cin,std::cout;
inline bool isInteger(char a){
if(a>='0'&&a<='9') return true;
else return false;
}
inline char Conv(int a){
return (a+'0');
}
inline int Conv(char a){
return (a-'0');
}
/*
* UorL == 1 => fill lowers;
* UorL == 2 => fill uppers;
* UorL == 3 => fill '*';
*
* repeat means how many times the char would be repeat filled
*
* revert == 1 => filled normally
* revert == 2 => filled reversely
*/
std::string filling(char left,char right, int UorL, int repeat, int revert){
// int size = right - left;
std::string filling;
if(revert == 1)
for (char t{char(left+1)}; right-t > 0 ;t++)
{
for (int j = 0; j < repeat; j++)
{
if(UorL==3){
filling+='*';
}
else if(UorL==1||isInteger(left)){ //single-side detect since already checked outside;
filling+=t;
}
else if(UorL==2){
filling+=toupper(t);
}
}
}
if(revert == 2)
for (char t{char(right-1)}; t-left > 0 ;t--)
{
for (int j = 0; j < repeat; j++)
{
if(UorL==3){
filling+='*';
}
else if(UorL==1||isInteger(left)){ //single-side detect since already checked outside;
filling+=t;
}
else if(UorL==2){
filling+=toupper(t);
}
}
}
return filling;
}
//UorL == Upper or Lower
std::string extendString(std::string& input,int UorL = 1,int repeat = 1,int revert = 1){
char left,right;
std::string output;
std::string::iterator it = input.begin();it++;
while(it-1<input.end()){
left = *(it-1);
right = *(it+1);
output+=left;
if(*it=='-'){
if(!(islower(left)&&islower(right))&&!(isInteger(left)&&isInteger(right))){
it++;
continue;
}
if(right - left == 1){
//input.erase(it);
it++;
}
//if(*it=='c'){;}
else if((right - left)>1){
//input.replace(it,it+1,filling(left,right,UorL,repeat,revert));//filling(left,right,UorL,repeat,revert)
output+=filling(left,right,UorL,repeat,revert);
it++;
}
}
it++;
}
return output;
}
int main(){
std::string input;
int p1,p2,p3;
cin>>p1>>p2>>p3;
cin>>input;
cout<<extendString(input,p1,p2,p3);
return 0;
}
实时输出
#include<iostream>
using std::cin,std::cout;
inline bool isInteger(char a){
if(a>='0'&&a<='9') return true;
else return false;
}
inline char Conv(int a){
return (a+'0');
}
inline int Conv(char a){
return (a-'0');
}
/*
* UorL == 1 => fill lowers;
* UorL == 2 => fill uppers;
* UorL == 3 => fill '*';
*
* repeat means how many times the char would be repeat filled
*
* revert == 1 => filled normally
* revert == 2 => filled reversely
*/
void filling(char left,char right, int UorL, int repeat, int revert){
if(revert == 1)
for (char t{char(left+1)}; right-t > 0 ;t++)
{
for (int j = 0; j < repeat; j++)
{
if(UorL==3){
cout<<'*';
}
else if(UorL==1||isInteger(left)){ //single-side detect since already checked outside;
cout<<t;
}
else if(UorL==2){
cout<<char(toupper(t));
}
}
}
if(revert == 2)
for (char t{char(right-1)}; t-left > 0 ;t--)
{
for (int j = 0; j < repeat; j++)
{
if(UorL==3){
cout<<'*';
}
else if(UorL==1||isInteger(left)){ //single-side detect since already checked outside;
cout<<t;
}
else if(UorL==2){
cout<<char(toupper(t));
}
}
}
return;
}
//UorL == Upper or Lower
void extendString(std::string& input,int UorL = 1,int repeat = 1,int revert = 1){
char left,right;
std::string::iterator it = input.begin();it++;
while(it-1<input.end()){
left = *(it-1);
right = *(it+1);
cout<<left;
if(*it=='-'){
if(!(islower(left)&&islower(right))&&!(isInteger(left)&&isInteger(right))){
it++;
continue;
}
if(right - left == 1){
it++;
}
else if((right - left)>1){
filling(left,right,UorL,repeat,revert);
it++;
}
}
it++;
}
return;
}
int main(){
std::string input;
int p1,p2,p3;
cin>>p1>>p2>>p3;
cin>>input;
extendString(input,p1,p2,p3);
return 0;
}