Problem p02269 (C++)

Buggy submission (status: Runtime Error):
//
//  main.cpp
//  dictionary
//
//  Created by ???????????? on 2017/10/06.
//  Copyright ?? 2017 ????????????. All rights reserved.
//

#include <cmath>
#include <cstring>
#include <iostream>
#include <stdio.h>

#define NIL (0)

using namespace std;

int m = 10000000;

int char_to_int(char str) {
  if (str == 'A') {
    return 1;
  } else if (str == 'C') {
    return 2;
  } else if (str == 'G') {
    return 3;
  } else if (str == 'T') {
    return 4;
  }
  cout << "Unexpected input given" << endl;
  return 0;
}

long long get_key(char string[]) {
  long long key_str = 0, p = 1;
  size_t n = strlen(string);
  for (int i = 0; i < n; i++) {
    key_str += p * char_to_int(string[i]);
    p *= 5;
  }
  return key_str;
}

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

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

int h(int key, int i) { return (h1(key) + i * h2(key)) % m; }

void insert(int T[], int key) {
  int i = 0;
  while (true) {
    int j = h(key, i);
    if (T[j] == NIL) {
      T[j] = key;
      break;
    } else {
      i++;
    }
  }
}

bool search(int T[], int key) {
  int i = 0;
  while (true) {
    int j = h(key, i);
    if (T[j] == key) {
      return true;
    } else if (T[j] == NIL || i > m) {
      return false;
    } else {
      i++;
    }
  }
}

int main(int argc, const char *argv[]) {
  int n, i;
  long long key;
  char com[10], string[10];
  int T[m];

  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%s %s", com, string);
    key = get_key(string);
    if (com[0] == 'i') {
      insert(T, key);
    } else if (com[0] == 'f') {
      if (search(T, key)) {
        cout << "yes" << endl;
      } else {
        cout << "no" << endl;
      }
    } else {
      cout << "Got unexpected command" << endl;
    }
  }

  return 0;
}

Fixed submission:
//
//  main.cpp
//  dictionary
//
//  Created by ???????????? on 2017/10/06.
//  Copyright ?? 2017 ????????????. All rights reserved.
//

#include <cmath>
#include <cstring>
#include <iostream>
#include <stdio.h>

#define NIL (0)

using namespace std;

int m = 1046527;

int char_to_int(char str) {
  if (str == 'A') {
    return 1;
  } else if (str == 'C') {
    return 2;
  } else if (str == 'G') {
    return 3;
  } else if (str == 'T') {
    return 4;
  }
  cout << "Unexpected input given" << endl;
  return 0;
}

long long get_key(char string[]) {
  long long key_str = 0, p = 1;
  size_t n = strlen(string);
  for (int i = 0; i < n; i++) {
    key_str += p * char_to_int(string[i]);
    p *= 5;
  }
  return key_str;
}

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

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

int h(int key, int i) { return (h1(key) + i * h2(key)) % m; }

void insert(int T[], int key) {
  int i = 0;
  while (true) {
    int j = h(key, i);
    if (T[j] == NIL) {
      T[j] = key;
      break;
    } else {
      i++;
    }
  }
}

bool search(int T[], int key) {
  int i = 0;
  while (true) {
    int j = h(key, i);
    if (T[j] == key) {
      return true;
    } else if (T[j] == NIL || i > m) {
      return false;
    } else {
      i++;
    }
  }
}

int main(int argc, const char *argv[]) {
  int n, i;
  long long key;
  char com[10], string[10];
  int T[m];

  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%s %s", com, string);
    key = get_key(string);
    if (com[0] == 'i') {
      insert(T, key);
    } else if (com[0] == 'f') {
      if (search(T, key)) {
        cout << "yes" << endl;
      } else {
        cout << "no" << endl;
      }
    } else {
      cout << "Got unexpected command" << endl;
    }
  }

  return 0;
}