public static void backTracking(int targetSum, int k, int startIndex, int sum) { // 减枝 if (sum > targetSum) { return; } if (startIndex-path.size() >2) { return; }else if (sum == targetSum){ count++; return; } for (int i = startIndex; i < nums.length; i++) { path.add(i); sum += nums[i]; backTracking(targetSum, k, i + 1, sum); path.removeLast(); sum -= nums[i]; 把分数存成一个数组,10个2,10个4,5个8,从0开始,然后回溯