Difference Array Concept

🧠 Concept

• Difference of current element of previous element for each slot

• Add or subtract value to a range of elements frequently

• 区间增减

• class Difference {
      private int[] diff;
  
      public Difference(int[] nums) {
          diff = new int[nums.length];
  
          diff[0] = nums[0];
          for (int i = 1; i < nums.length; i++) {
              diff[i] = nums[i] - nums[i - 1];
          }
      }
  
      // 给闭区间 [i, j] 增加 val（可以是负数）
      public void increment(int i, int j, int val) {
          diff[i] += val;
          if (j + 1 < diff.length) {
              diff[j + 1] -= val;
          }
      }
  
      public int[] result() {
          int[] res = new int[diff.length];
  
          res[0] = diff[0];
          for (int i = 1; i < diff.length; i++) {
              res[i] = res[i - 1] + diff[i];
          }
  
          return res;
      }
  }