我试图让这个合并排序函数对向量或单词节点进行排序（包含单词长度、出现次数和单词本身）似乎进入合并函数一次，然后程序失败，有什么想法吗？
bool Utility::mergeSort_occurences(vector<Word> &invector){
if (invector.size() <= 1){
return true;
}
vector<Word> left, right;
int middle = (invector.size()/2);
for(int i = 0 ; i < middle ; i++){
left.push_back(invector[i]);
}
for(int i = middle ; i < invector.size() ; i++){
right.push_back(invector[i]);
}
mergeSort_occurences(left);
mergeSort_occurences(right);
invector = mergeOccurences(left, right);
return true;
}
vector<Word> Utility::mergeOccurences(vector<Word> &left, vector<Word> &right){
vector<Word> mergelist;
while(left.size() > 0 || right.size() > 0){
if(left.size() > 0 && right.size() > 0){
if(left[0].getOccurences() <= right[0].getOccurences()){
mergelist.push_back(left[0]);
left.erase(left.begin());
}else{
mergelist.push_back(right[0]);
right.erase(right.erase(right.begin()));
}
}
else if(left.size() > 0){
mergelist.push_back(left[0]);
left.erase(left.begin());
}
else if(right.size() > 0){
mergelist.push_back(right[0]);
right.erase(right.erase(right.begin()));
}
}
return mergelist;
}