7.4 KiB
7.4 KiB
知识点
好的，我将为你系统整理这四章的全部知识点，按章节顺序分解并整合核心内容、定义、图示、流程图，并汇总例题。对于每章内容，我也会根据重点举一反三地出一些典型练习题并附上解析，帮助你理解和练习。 我完成后会通知你查看结果。
编程题
A
#include <bits/stdc++.h>
using namespace std;
string S[]={"main","if","else","for","while","int"};
void show(string s){
if(s[0]>='0'&&s[0]<='9')
cout << "(integer," << s << ")" << endl;
else{
int flag=0;
for(int i=0;i<6;i++){
if(s==S[i]){
flag=1;
cout<<"(keyword,"<<s<<")"<<endl;
}
}
if(flag==0)
cout<<"(identifier,"<<s<<")"<<endl;
}
}
int main()
{
string s;
while (cin >> s)
{
int len = s.length();
string a = "";
for (int i = 0; i < len; i++)
{
if (s[i] == '=' || s[i] == '+' || s[i] == '-' || s[i] == '*' || s[i] == '/' || s[i] == '<' || s[i] == '>' || s[i] == '!')
{
if (a.length())
show(a);
a = "";
if (i + 1 < len && s[i + 1] == '=')
{
cout << "(operator," << s[i] << s[i + 1] << ")" << endl;
i++; // i+1,否则下次循环会重复判断
}
else
cout << "(operator," << s[i] << ")" << endl;
}else if(s[i]=='('||s[i]==')'||s[i]=='{'||s[i]=='}'||s[i]==','||s[i]==';'){
if(a.length())
show(a);
a="";
cout << "(boundary," << s[i] << ")" << endl;
}else
a+=s[i];
}
if(a.length())
show(a);
}
}
两个特殊点
- 就是分类要分好
- 通过show()函数来将a给打印出来 这样打印其他（operator||boundary）的时候能打印干净
B
#include <bits/stdc++.h>
#include <regex>
using namespace std;
int main()
{
string s;
cin >> s;
regex pattern(R"(^[+-]?((\d+\.\d+)([eE][+-]?\d+)?|(\d+)[eE][+-]?\d+)$)");
cout << (regex_match(s, pattern) ? "YES\n" : "NO\n");
return 0;
}
// R"(^[\t]*[+-]?)"
// 1) 小数（两侧有数字）^[\t]* [+-]?((\d\.\d) + 可选指数 ([eE][+-]?\d)?)
// 2) 整数 + 必须指数
// R"( ^[+-]? ( (\d+\.\d+) ([eE][+-]?\d+)? | (\d+)([eE][+-]?\d+) )$ )" //^[+-]?可选正负号
//(\d+\.\d+)任意小数
//([eE][+-]?\d+)?可选指数
//(\d+)任意整数
//[eE][+-]?\d+ 必须整数
//R"(^[+-]?( (\d+\.\d+)([eE][+-]?\d+)? | (\d+)[eE][+-]?\d+ ) )"
C
#include <bits/stdc++.h>
using namespace std;
struct Node {
string s1, s2;
};
Node p[101];
int var[26];
int expression(const string& s) {
if (s.length() >= 3 && (s[1] == '+' || s[1] == '>')) {
int a = s[0] - 'A';
int b = s[2] - 'A';
if (s[1] == '+') return var[a] + var[b];
else return var[a] > var[b];
}
if (s[0] == '-') return -stoi(s.substr(1));
return stoi(s);
}
int main() {
int n, max_line = 0;
string s1, s2;
memset(var, 0, sizeof(var));
while (cin >> n) {
cin >> s1;
p[n].s1 = s1;
if (s1 != "STOP") {
cin >> s2;
p[n].s2 = s2;
}
max_line = max(max_line, n); // 记录最大行号
}
for (int i = 1; i <= max_line; i++) {
if (p[i].s1.empty()) continue;
string cmd = p[i].s1, arg = p[i].s2;
if (cmd == "LET") {
int idx = arg[0] - 'A';
var[idx] = expression(arg.substr(2));
} else if (cmd == "PRINT") {
int idx = arg[0] - 'A';
cout << arg[0] << "=" << var[idx] << endl;
} else if (cmd == "GOTO") {
i = expression(arg) - 1;
} else if (cmd == "IF") {
if (!expression(arg)) i++;
} else if (cmd == "STOP") {
break;
}
}
}
D
#include <bits/stdc++.h>
using namespace std;
/*
E→TG
G→+TG | ε
T→FS
S→*FS | ε
F→(E) | i
*/
void E();
void G();
void T();
void S();
void F();
int num = 0;
int idx = 0;
string s;
void E()
{
if (s[idx] == '(' || s[idx] == 'i')
{
cout << num++ << " E-->TG" << endl;
T();
G();
}
else
{
puts("error");
exit(0);
}
}
void G()
{
if (s[idx] == '+')
{
cout << num++ << " G-->+TG" << endl;
idx++;
T();
G();
}
else
{
cout << num++ << " G-->&" << endl;
}
}
void T()
{
if (s[idx] == '(' || s[idx] == 'i')
{
cout << num++ << " T-->FS" << endl;
F();
S();
}
else
{
puts("error");
exit(0);
}
}
void S()
{ // S→*FS | ε
if (s[idx] == '*')
{
cout << num++ << " S-->*FS" << endl;
idx++;
F();
S();
}
else
{
cout << num++ << " S-->&" << endl;
}
}
void F()
{
if (s[idx] == '(')
{
cout << num++ << " F-->(E)" << endl;
idx++;
E();
if (s[idx] == ')')
idx++;
else
{
cout << "error" << endl;
exit(0);
}
}
else if (s[idx] == 'i')
{
cout << num++ << " F-->i" << endl;
idx++;
}
else
{
puts("error");
exit(0);
}
}
int main()
{
cin >> s;
E();
if (s[idx] == '#')
cout << "accept" << endl;
else
cout << "error" << endl;
}
E
#include <bits/stdc++.h>
using namespace std;
char s[100];
int c = 0;
int num = 1;
void E();
void T();
void G();
void F();
void S();
void E() // E→TG
{
if (s[c] == 'i' || s[c] == '(')
{
cout << num++ << " E->TG" << endl;
T();
G();
}
else
{
puts("error!");
exit(0);
}
}
// G→+TG | ε
void G()
{
if (s[c] == '+')
{
cout << num++ << " G->+TG" << endl;
c++; // 注意这里因为一s[c]一定是+ 那么下一次判断也就是
// T() 和G()判断的时候 就应该从s[c++]开始 所以c++
T();
G();
}
else if (s[c] == ')' || s[c] == '#')
{
cout << num++ << " G->^" << endl; // 只有在 FOLLOW(G) 才能走 ε
}
else
{
puts("error!");
exit(0);
}
}
void T() // T→FS
{
if (s[c] == 'i' || s[c] == '(')
{
cout << num++ << " T->FS" << endl;
F();
S();
}
else
{
cout << "error!" << endl;
exit(0);
}
}
void S() // S→*FS | ε
{
if (s[c] == '*')
{
cout << num++ << " S->*FS" << endl;
c++;
F();
S();
}
else if (s[c] == '+' || s[c] == ')' || s[c] == '#')
{
cout << num++ << " S->^" << endl; // 只有在 FOLLOW(S) 才能走 ε
}
else
{
puts("error!");
exit(0);
}
}
void F()
{
if (s[c] == 'i')
{
cout << num++ << " F->i" << endl;
c++;
}
else if (s[c] == '(')
{
cout << num++ << " F->(E)" << endl;
c++;
E();
if (s[c] == ')')
c++;
else
{
cout << "error!" << endl;
exit(0);
}
}
else
{
cout << "error!" << endl;
exit(0);
}
}
int main()
{
cin >> s;
E();
if (s[c] != '#')
cout << "error!" << endl;
else
cout << "acc!" << endl;
}