Create 0303-range-sum-query-immutable.ts

Author: KhanShaheb34

typescript/0303-range-sum-query-immutable.ts

@@ -0,0 +1,22 @@
+class NumArray {
+
+    prefixSums: number[] = [];
+
+    constructor(nums: number[]) {
+        this.prefixSums.push(nums[0]);
+
+        for(let i=1; i<nums.length; i++)
+            this.prefixSums.push(this.prefixSums[i-1] + nums[i])
+    }
+
+    sumRange(left: number, right: number): number {
+        if(left === 0) return this.prefixSums[right];
+        return this.prefixSums[right] - this.prefixSums[left-1];
+    }
+}
+
+/**
+ * Your NumArray object will be instantiated and called as such:
+ * var obj = new NumArray(nums)
+ * var param_1 = obj.sumRange(left,right)
+ */