### LeetCode - Range Sum Query Immutable Solution - The Coding Shala

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In this post, we will learn how to solve LeetCode's Range Sum Query Immutable Problem and its solution in Java.

## Range Sum Query Immutable Problem

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. Implement the NumArray class:
NumArray(int[] nums) Initializes the object with the integer array nums. int sumRange(int i, int j) Return the sum of the elements of the nums array in the range [i, j] inclusive (i.e., sum(nums[i], nums[i + 1], ... , nums[j])).

Example 1:
Input: ["NumArray", "sumRange", "sumRange", "sumRange"]
[[[-2, 0, 3, -5, 2, -1]], [0, 2], [2, 5], [0, 5]]
Output: [null, 1, -1, -3]

## Range Sum Query - Immutable Java Solution

Approach 1:
First, make a sum array that contains sum till every index then return sum[j] - sum[i-1].

Java Program:

```class NumArray {

int len;
int[] sum;

public NumArray(int[] nums) {
this.len = nums.length;
sum = new int[len];
for(int i=0;i<len;i++){
if(i==0) sum[0] = nums[0];
else sum[i] = nums[i] + sum[i-1];
}
}

public int sumRange(int i, int j) {
if(i==0) return sum[j];
return (sum[j]-sum[i-1]);
}
}

/**
* Your NumArray object will be instantiated and called as such:
* NumArray obj = new NumArray(nums);
* int param_1 = obj.sumRange(i,j);
*/
```

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