PAT/PATAdvanced/1035.c

#include <stdio.h>

int main()
{
    int N, count = 0, modified;
    char username[1000][11], password[1000][11];

    scanf("%d", &N);
    for(int i = 0; i < N; i++)
    {
        modified = 0;
        scanf("%s %s", username[i], password[i]);
        for(char *p = password[i]; *p; p++)
        {
            switch(*p)
            {
                case '1': *p = '@'; modified = 1; break;
                case '0': *p = '%'; modified = 1; break;
                case 'l': *p = 'L'; modified = 1; break;
                case 'O': *p = 'o'; modified = 1; break;
                default: break;
            }
        }
        if(modified)
            count++;
        else  /* mark unmodified password */
            password[i][0] = '\0';
    }

    if(count)
    {
        printf("%d\n", count);
        for(int i = 0; i < N; i++)
            if(password[i][0] != '\0')
                printf("%s %s\n", username[i], password[i]);
    }
    else
    {
        printf("There %s %d %s and no account is modified",
            N > 1 ? "are" : "is", N, N > 1 ? "accounts" : "account");
    }

    return 0;
}