LeetCode刷题之数组链表

• 前缀和技巧

  前缀和技巧适用于的场景是原始数组不会被修改的情况下，频繁地查询某个区间地累加和。

  大致框架如下所示：

  class preSum{
  public:
      vector<int> sums;
      
      preSum(vector<int>& nums) {
          int len = nums.size();
          sums.resize(len + 1);
          for (int i = 0; i < len; i++) {
              sums[i + 1] = sums[i] + nums[i];
          }
      }
      
      int getSum(int left, int right) {
          return sums[right + 1] - sums[left];
      }
      
  }
  

  LeetCode例题 303 304 560

• 差分数组

  差分数组主要适用于对原数组地某个区间的元素进行频繁的增减。

  大致框架如下：

  class Difference{
  private:
      vector<int> diff;
      
  public:
      Difference(vector<int>& nums) {
          assert(nums.size() > 0);
          int len = nums.size();
          diff.resize(len);
          diff[0] = nums[0];
          for (int i = 1; i < len; i++) {
              diff[i] = nums[i] - nums[i - 1];
          }
      }
      
      void increment(int i, int j, int val) {
           diff[i] += val;
          if (j + 1 <diff.size()) {
              diff[j + 1] -= val;
          }
      }
      
      vector<int> getResult() {
          vector<int> result;
          result[0] = diff[0];
          for (int i = 1; i < diff.size(); i++) {
              result[i] = diff[i] + diff[i - 1];
          }
          return result;
      }
  }
  

  LeetCode例题有1109和1094

标签：nums,int,sums,len,链表,vector,diff,LeetCode,刷题
来源： https://www.cnblogs.com/iubolgs/p/15905183.html