Laboratory task 2

#include <stdio.h>
#include <string.h>

// Examples in comments for (var1+(var2*(a-b)))
char lexemes[256][256];  // {"(", "var1", "(", "var2", "*", "(", "a", "-", "b", ")", ")", ")"}
char expression[256]; // "(var1+(var2*(a-b)))"
int indexesOfIdenteficators[256];  // Indexes of lexemes: {1, 3, 6, 8}. lexemes[1] = "var1", lexemes[3] = "var2", lexemes[6] = "a", lexemes[8] = "b"
int lenLexemes = 0, lenExpression, lenIndexesOfIdenteficators = 0;  // Sizes


int is_alpha(char c) { return ('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z'); }


int is_digit(char c) { return ('0' <= c && c <= '9'); }


int is_sign(char c) { return (c == '+' || c == '-' || c == '*' || c == '/'); }


int find_right_by_identeficator(int l) {  // Return int marked to right border if it can be identificator
    if (is_alpha(expression[l])) {
        for (int i = l + 1; i <= lenExpression; ++i) {
            if (i == lenExpression || !is_alpha(expression[i]) && !is_digit(expression[i]) && expression[i] != '_')  // If i`s symbol incorrect for identeficator
                return i - 1;
        }
    } return -1;
}


int find_right_by_number(int l) {  // Return int marked to right border if it can be number
    if (is_digit(expression[l])) {
        for (int i = l + 1; i <= lenExpression; ++i) {
            if (i == lenExpression || !is_digit(expression[i])) return i - 1;
        }
    } return -1;
}


int is_simple_exp(int l, int r) {  // Is expression[l]...expression[r] a <simpleExp>?
    int ril = find_right_by_identeficator(l), rnl = find_right_by_number(l);
    if (expression[l] == '(' && expression[r] == ')') {  // If simpleExp = (<simpleExp><sign><simpleExp>)
        int signIndex = -1;
        lexemes[lenLexemes][0] = '(';
        lexemes[lenLexemes++][1] = '\0';
        for (int i = l + 1; i < r; ++i) {
            if (is_sign(expression[i])) {
                signIndex = i;
                break;
            }
        }
        if (signIndex == -1) return 0;
        int res1 = is_simple_exp(l + 1, signIndex - 1);  // Process first simpleExp
        lexemes[lenLexemes][0] = expression[signIndex];
        lexemes[lenLexemes++][1] = '\0';
        int res2 = is_simple_exp(signIndex + 1, r - 1);  // Process second simpleExp
        lexemes[lenLexemes][0] = ')';
        lexemes[lenLexemes++][1] = '\0';
        return res1 && res2;  // If res1 == 0 then res2 may be not run
    } if (ril == r) {  // If simpleExp = <identeficator>
        for (int i = l; i <= ril; ++i) {  // Add identeficator by index l to ril
            lexemes[lenLexemes][i - l] = expression[i];
        } lexemes[lenLexemes++][ril - l + 1] = '\0';
        indexesOfIdenteficators[lenIndexesOfIdenteficators++] = lenLexemes - 1;
        return 1;
    } if (rnl == r) { // If simpleExp = <numeric value>
        for (int i = l; i <= rnl; ++i) {  // Add number by index l to rnl
            lexemes[lenLexemes][i - l] = expression[i];
        } lexemes[lenLexemes++][rnl - l + 1] = '\0';
        return 1;
    }
    return 0;
}


void print_lexemes() {  // Technical function
    for (int i = 0; i < lenLexemes; ++i) printf("%s", lexemes[i]);
    putchar('\n');
}


int main() {
    freopen("input.txt", "r", stdin);
    char identeficators[256][256], numericValues[256][256];
    int N;
    scanf("%d", &N);
    for (int i = 0; i < N; ++i) scanf("%s %s", identeficators[i], numericValues[i]);
    scanf("%s", expression);
    lenExpression = strlen(expression);

    if (!is_simple_exp(0, lenExpression - 1)) {
        printf("INCORRECT\n");
        return 0;
    }
    for (int i = 0; i < lenIndexesOfIdenteficators; ++i) {
        for (int j = 0; j < N; ++j) {
            if (!strcmp(lexemes[indexesOfIdenteficators[i]], identeficators[j])) {  // If need replace (names equal)
                for (int q = 0; q < strlen(numericValues[j]); ++q)  // Replace character by character
                    lexemes[indexesOfIdenteficators[i]][q] = numericValues[j][q];
                lexemes[indexesOfIdenteficators[i]][strlen(numericValues[j])] = '\0';
            }
        }
    }

    print_lexemes();  // Print current replaced expression
    return 0;
}