Language: C++

#include <iostream>
using namespace std;

static const int MAX = 1000003;
static const int STRLEN = 13;
static const int CMDLEN = 7;
static const int KEYLEN = 14;

char H[MAX][KEYLEN];

int h1(int key) {
    return key % MAX;
}

int h2(int key) {
    return 1 + (key % (MAX - 1));
}

int getChar(char c) {
    if (c == 'A') return 1;
    else if (c == 'C') return 2;
    else if (c == 'G') return 3;
    else if (c == 'T') return 4;
    else return 0;
}

long long getKey(char str[]) {
    long long sum = 0, p = 1;
    for (int i = 0; i < strlen(str); i++) {
        sum += p * (getChar(str[i]));
        p *= 5;
    }
    return sum;
}

int find(char str[]) {
    long long key, i = 0, h;
    key = getKey(str);
    while (1) {
        h = (h1(key) + i * h2(key)) % MAX;
        if (strcmp(H[h], str) == 0) {
            return 1;
        } else if (strlen(H[h]) == 0) {
            return 0;
        }
        i++;
    }
    return 0;
}

int insert(char str[]) {

    long long key, i = 0, h;
    key = getKey(str);
    while (1) {
        h = (h1(key) + i * h2(key)) % MAX;
        if (strcmp(H[h], str) == 0) {
            return 1;
        } else if (strlen(H[h]) == 0) {
            strcpy(H[h], str);
            return 0;
        }
        i++;
    }

    return 0;
}



int main (void) {
    int n;
    cin >> n;

    // initialize
    for (int i = 0; i < MAX; i++) {
        H[i][0] = '\0';
    }

    char str[STRLEN], cmd[CMDLEN];
    for (int i = 0; i < n; i++) {
        cin >> cmd >> str;

        if (cmd[0] == 'i') {
            insert(str);
        } else if (cmd[0] == 'f') {
            if (find(str)) {
                cout << "yes" << endl;
            } else {
                cout << "no" << endl;
            }
        }
    }

    return 0;
}

Compiler output:
a.cc: In function 'long long int getKey(char*)':
a.cc:29:25: error: 'strlen' was not declared in this scope
   29 |     for (int i = 0; i < strlen(str); i++) {
      |                         ^~~~~~
a.cc:2:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    1 | #include <iostream>
  +++ |+#include <cstring>
    2 | using namespace std;
a.cc: In function 'int find(char*)':
a.cc:41:13: error: 'strcmp' was not declared in this scope
   41 |         if (strcmp(H[h], str) == 0) {
      |             ^~~~~~
a.cc:41:13: note: 'strcmp' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
a.cc:43:20: error: 'strlen' was not declared in this scope
   43 |         } else if (strlen(H[h]) == 0) {
      |                    ^~~~~~
a.cc:43:20: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
a.cc: In function 'int insert(char*)':
a.cc:57:13: error: 'strcmp' was not declared in this scope
   57 |         if (strcmp(H[h], str) == 0) {
      |             ^~~~~~
a.cc:57:13: note: 'strcmp' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
a.cc:59:20: error: 'strlen' was not declared in this scope
   59 |         } else if (strlen(H[h]) == 0) {
      |                    ^~~~~~
a.cc:59:20: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
a.cc:60:13: error: 'strcpy' was not declared in this scope
   60 |             strcpy(H[h], str);
      |             ^~~~~~
a.cc:60:13: note: 'strcpy' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'