注意off by 1 还有里面for loop别加错index
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21 | public class Solution {
public List<List<Integer>> generate(int numRows) {
List<List<Integer>> result = new ArrayList<List<Integer>>();
if (numRows <= 0) return result;
List<Integer> firstRow = new ArrayList<Integer>();
firstRow.add(1);
result.add(firstRow);
for (int i = 1; i < numRows; i++){
List<Integer> prevRow = result.get(i-1);
List<Integer> current = new ArrayList<Integer>();
current.add(1);
for (int j = 1; j <= i; j++){
int upLeft = prevRow.get(j-1);
int upper = prevRow.size() == j?0:prevRow.get(j);
current.add(upLeft+upper);
}
result.add(current);
}
return result;
}
}
|
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