# 370. Range Addition (差分

T: O(k + n), k is size of updates, n is the length

S: O(n)

```java
class Solution {
    public int[] getModifiedArray(int length, int[][] updates) {
        int[] res = new int[length];
        
        for (int[] update : updates) {
            int startIdx = update[0];
            int endIdx = update[1];
            int value = update[2];
            res[startIdx] += value;
            
            if (endIdx < length - 1) {
                res[endIdx + 1] -= value;
            }
        }
        
        int sum = 0;
        for (int i = 0; i < length; i++) {
            sum += res[i];
            res[i] = sum;
        }
        return res;
    }
}

/*

for example it will look like:

[1 , 3 , 2] , [2, 3, 3] (length = 5)


record number at start,
record negtive number out of ending (end+1) => key point
then use prefix sum add -> it's result
  
0 1 2 3 4 5
  2 2 2
    3 3

0 2 0 0 -2
    3   -3
    
[[1,3,2],[2,4,3],[0,2,-2]]


 0 1 2 3 4 5
   2     -2  
     3     -3 => no need record (last index)
-2     2

-2 0 3 5  3 

    
*/
```

### diff new version

```java
class Solution {
    public int[] getModifiedArray(int length, int[][] updates) {
        int[] diff = new int[length];
        for (int[] update : updates) {
            int start = update[0];
            int end = update[1];
            int inc = update[2];
            
            diff[start] += inc;
            if (end + 1 < length) {
                diff[end+1] -= inc;
            }
        }
        int[] result = new int[length];
        result[0] = diff[0];
        for (int i = 1; i < length; i++) {
            result[i] = result[i-1] + diff[i];
        }
        return result;
    }
}

/*

diff[i] = nums[i] - nums[i-1]

so nums[i] = diff[i] + nums[i-1], so if change diff , the interval value will change, 
so diff[i] += number, and do diff[j+1] -= number


[0, 2,2,2,0 ]

diff[i] +=2 , diff[1] = 2
diff[j+1] -= 2 diff[4] = -2


res[i] = res[i-1] + diff[i]

 0 0 0 0 0
   1
 
 res[0] = 0
 res[1] = 2
 res[2] = res[1] + diff[2](0) = 2
 res[3] = res[2] + diff[3](0) = 2
 res[4] = res[3] + diff[4](-2) = 0

*/
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://timmybeeflin.gitbook.io/cracking-leetcode/prefix-sum/diff-array-cha-fen/370.-range-addition-cha-fen.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.