一维

 public static class indexTree {
        //辅助数组
        private int[] tree;
        private int N;
        public indexTree(int size) {
            N = size;
            tree = new int[N + 1];
        }
        // 0 ~ index 范围上的累加和
        public int sum(int index) {
            int res = 0;
            while (index > 0) {
                res += tree[index];
                index -= index & -index;
            }
            return res;
        }
        // index位置的数，想加上d，还有哪些位置也要都加d
        public void add(int index, int d) {
            while (index <= N) {
                tree[index] += d;
                index += index & -index;
            }
        }
    }

二维

308题

三维