【leetcode】键盘行

char ** findWords(char ** words, int wordsSize, int* returnSize){
    char* symbol[] = {"123456789","qwertyuiop","asdfghjkl","zxcvbnm"};
    char** arr = (char**)malloc(wordsSize*sizeof(char*));
    int i,j,k,pst,n=0;
    for (i=0; i<wordsSize; i++)
    {
        pst=0;
        for (j=0; j<strlen(words[i]); j++)
        {
            if (pst) 
            {
                if (!strchr(symbol[pst],tolower(words[i][j]))) break;
            }
            else
            {
                for (k=1; k<=3; k++)
                    if (strchr(symbol[k],tolower(words[i][j]))) pst=k;
            }            
        }
        if (j == strlen(words[i]))
            arr[n++] = words[i];
    }
    *returnSize=n;
    return arr;
}