G家的一道题，属于会者不难的那种，一个要点是remaining column要从 total column 往下减，而不是从 0 往上加。同时，要用除和取mod，来节省时间。
int wordsTyping(vector<string>& sentence, int rows, int cols) {
if(sentence.empty()) return rows * cols;
int row = 1, col = cols, idx = 0, cnt = 0;
int total_len = 0;
for(int i=0; i<sentence.size(); i++){
total_len += sentence[i].length()+1;
}
while(row <= rows){
if(col >= sentence[idx].length()){
col = col - sentence[idx].length();
if(col > 0) col--;
if(++idx == sentence.size()){
cnt += (1 + col/total_len);
col = col % total_len;
idx = 0;
}
}else{
row++; col = cols;
}
}
return cnt;
}
