https://leetcode-cn.com/problems/he-wei-sde-lian-xu-zheng-shu-xu-lie-lcof/

我的解，暴力枚举

  1. class Solution {
  2. public:
  3.     vector<vector<int>> findContinuousSequence(int target) {
  4.         vector<vector<int>> result;
  5.         vector<int> vec;
  6.         int start = 1;
  7.         for (int i = 1; i <= (target/2)+1;++i) {
  8.             int sum = 0;
  9.             for (int j = i; j <= (target/2)+1; ++j) {
  10.                 sum += j;
  11.                 if (sum == target) {
  12.                     vec.push_back(j);
  13.                     result.push_back(vec);
  14.                     vec.clear();
  15.                     break;
  16.                 }
  17.                 else if (sum < target) {
  18.                     if (sum+i > target) {
  19.                         vec.clear();
  20.                         break;
  21.                     }
  22.                     else {
  23.                         vec.push_back(j);
  24.                     }
  25.                 }
  26.                 else {
  27.                     vec.clear();
  28.                     break;
  29.                 }
  30.             }
  31.         }
  32.         return result;
  33.     }
  34. };

官方双指针解

  • sum 值通过求和公式得

  • 如果 sum 等于目标值则情况临时数组并将区间 [l,r] 内所有值写入其中，然后结果数组push这个临时数组，左指针++

  • 如果 sum 大于目标，则左指针右移
  • sum 小于目标，右指针右移
    class Solution {
public:
  vector<vector<int>> findContinuousSequence(int target) {
      vector<vector<int>>vec;
      vector<int> res;
      for (int l = 1, r = 2; l < r;){
          int sum = (l + r) * (r - l + 1) / 2;
          if (sum == target) {
              res.clear();
              for (int i = l; i <= r; ++i) {
                  res.emplace_back(i);
              }
              vec.emplace_back(res);
              l++;
          } else if (sum < target) {
              r++;
          } else {
              l++;
          }
      }
      return vec;
  }
};