1000. 词法分析程序设计 **

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问题描述

Description
设一语言的关键词、运算符、分界符的个数与单词如下：
struct { int number; string str[10]; } keywords={3,”int”,”main”,”return”} ; //关键词
struct { int number; string str[10]; } operators ={5,”+”,”“,”=”,”+=”,”=”}; //运算符
struct { int number; string str[10]; } boundaries ={6,”(“,”)”,”{“,”}”,”,”,”;”} ; //分界符
struct { int number; string str[100];} identifieres={0}; //标识符
struct { int number; string str[100];} Unsigned_integer={0}; //无符号整数
以上类号分别为1~5，序号从0开始；
标识符是字母开头的字母数字串；常量为无符号整数；
用C++设计一程序实现词法分析。

Input
输入一程序，结束符用”#”；

Output
输出单词数对：<类号，序号>。 输出标识符表，用空格分隔； 输出无符号整数表，用空格分隔；

Sample Input

main(){ int a=2,b=3;  return 2*b+a;}#

Sample Output

<1,1><3,0><3,1><3,2><1,0><4,0><2,2><5,0><3,4><4,1><2,2><5,1><3,5><1,2><5,0><2,1><4,1><2,0><4,0><3,5><3,3>identifieres:a bUnsigned_integer:2 3

Problem Source: 词法分析

实现

#include <iostream>#include <map>#include <string>using namespace std;struct { int number; string str[10]; } keywords = { 3,"int","main","return" }; //关键词struct { int number; string str[10]; } operators = { 5,"+","*","=","+=","*=" }; //运算符struct { int number; string str[10]; } boundaries = { 6,"(",")","{","}",",",";" }; //分界符struct { int number; string str[100]; } identifieres = { 0 }; //标识符struct { int number; string str[100]; } Unsigned_integer = { 0 }; //无符号整数int main() {    char c, temp;    int flag = 0;    while (1) {        if (flag == 1) {            c = temp;            flag = 0;        }        else if (flag == 0) {            cin.get(c);        }        if (c == '#') break;        if (c == ' ') continue;        for (int i = 0; i < boundaries.number; i++)  // 识别分解符            if (c == boundaries.str[i][0]) {                printf("<3,%d>", i);                continue;            }        // 识别运算符        if (c == '+' || c == '*') {            cin.get(temp);            if (temp == '=') {                if (c == '+') printf("<2,%d>", 3);                else printf("<2,%d>", 4);            }            else {                if (c == '+') printf("<2,%d>", 0);                else printf("<2,%d>", 1);                flag = 1;            }            continue;        }        else if (c == '=') {            printf("<2,%d>", 2);            continue;        }        // 识别无符号整数        string sint;        if (c >= '0' && c <= '9') {            sint.push_back(c);            while (1) {                cin.get(temp);                if (temp >= '0' && temp <= '9') {                    sint.push_back(temp);                }                else {                    flag = 1;                    break;                }            }            printf("<5,0>");            Unsigned_integer.str[Unsigned_integer.number++] = sint;            continue;        }        // 识别关键词和标识符        string ss;        if ((c >= 'a' && c <= 'z')||(c >= 'A' && c <= 'Z')) {  // 规定了标识符是字母开头, 不包含下划线            ss.push_back(c);            while (1) {                cin.get(temp);                if ((temp >= 'a' && temp <= 'z') || (temp >= 'A' && temp <= 'Z')||                    (temp >= '0' && temp <= '9')) {                    ss.push_back(temp);                }                else {                    flag = 1;                    break;                }            }            bool isKeyword = false;            for (int i = 0; i < keywords.number; i++) {                if (ss == keywords.str[i]) {                    printf("<1,%d>", i);                    isKeyword = true;                    break;                }            }            if (!isKeyword) {                printf("<4,0>");                identifieres.str[identifieres.number++] = ss;            }            continue;        }    }    printf("identifieres:");    for (int i = 0; i < identifieres.number; i++)        cout << identifieres.str[i] << " ";    printf("Unsigned_integer:");    for (int i = 0; i < Unsigned_integer.number; i++)        cout << Unsigned_integer.str[i] << " ";    return 0;}