[英]Adding numbers to first element of arrayLists
Suppose you have an arrayList of arrayLists: 假设您有一个arrayLists的arrayList:
[[a,b,6],[a,b,7],[s,d,3]]
I want to add a number as an index starting from 0 in first place of every arrayList
as long as the two first elements remains the same. 我想在每个arrayList
第一位添加一个数字作为索引,从0开始,只要两个第一元素保持相同即可。 When it doesn't, counting must start again from 0. So I expect as a result: 如果不是,则计数必须再次从0开始。因此,我期望得到这样的结果:
[[0,a,b,6],[1,a,b,7],[0,s,d,3]]
Any help is appreciated. 任何帮助表示赞赏。 Thanks 谢谢
You can iterate and remember the first two elements each step: 您可以迭代并记住每个步骤的前两个元素:
List<List<Object>> listOfLists = ...
Object first = listOfList.get(0).get(0);
Object second = listOfList.get(0).get(1);
int count = 0;
for (List<Object> list : listOfList) {
Object currFirst = list.get(0);
Object currSecond = list.get(1);
if (!currFirst.equals(first) || currSecond.equals(second)) {
first = currFirst;
second = currSecond;
count = 0;
}
list.add (0, count);
++count;
}
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