[leetcode]pascal's triangle

注意off by 1 还有里面for loop别加错index

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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; } }