What is the name for the sum of a contiguous block of elements within an array?

What is the name for the sum of a contiguous block of elements within an array?

• A. Subsequence Sum
• B. Prefix Sum
• C. Suffix Sum
• D. Total Sum

Answer: (A)

In arrays, the sum of a contiguous block of elements is called the subarray sum. A subarray is any consecutive run of elements, so summing that run gives the subarray sum. This is different from a subsequence, which preserves order but may skip elements, so its sum need not come from a consecutive block. For quick range sums, prefix sums are often used: if P[i] is the sum of the first i elements, then the sum from i to j is P[j] − P[i−1]. Prefix sums are building blocks for many range-sum problems, while suffix sums sum from a position to the end, and total sum adds up every element in the array. So the term for the sum of a contiguous block is subarray sum.

In arrays, the sum of a contiguous block of elements is called the subarray sum. A subarray is any consecutive run of elements, so summing that run gives the subarray sum. This is different from a subsequence, which preserves order but may skip elements, so its sum need not come from a consecutive block.

For quick range sums, prefix sums are often used: if P[i] is the sum of the first i elements, then the sum from i to j is P[j] − P[i−1]. Prefix sums are building blocks for many range-sum problems, while suffix sums sum from a position to the end, and total sum adds up every element in the array.

So the term for the sum of a contiguous block is subarray sum.