C语言中*(flow + i*n + j)是什么意思？求逻辑解析与概念指引

Hey there! Coming from Java, it makes total sense that this C/C++ pointer syntax feels confusing—Java hides a lot of this low-level memory stuff from you. Let's break down that line of code you encountered in your algorithms class step by step:

What's this operation called? #

This is pointer-based 2D array element access and modification. It's a classic trick in C/C++ to simulate a 2D matrix using a 1D array, since under the hood, 2D arrays in C/C++ are actually stored as contiguous blocks of memory anyway.

The Logic Explained #

Let's unpack each piece:

• flow is a pointer pointing to the start of a 1D array. This array is being used to represent an n x n matrix—given the variable names (flow, minFlowPath), this is almost certainly for a max-flow algorithm (like Edmonds-Karp or Ford-Fulkerson) where you're tracking flow capacities between nodes.
• i*n + j calculates how far we need to jump from the start of the array to reach the element at row i, column j:
  • Each row has n elements, so to get to row i, we skip i * n elements.
  • Adding j moves us to the exact column in that row.
• *(flow + i*n + j) grabs the value at that position (by dereferencing the pointer), and += minFlowPath adds the minimum flow from your augmenting path to it. In plain terms: you're updating the flow amount on the edge between node i and node j.

What's Being Stored? #

The 1D array pointed to by flow holds all elements of the n x n matrix in row-major order—meaning we store all elements of row 0 first, then row 1, then row 2, and so on until row n-1.

If you were using a "normal" 2D array in C/C++ (like int flow_2d[n][n];), this line would be exactly equivalent to writing flow_2d[i][j] += minFlowPath;. The pointer version is just a way to work with the underlying contiguous memory directly, which can sometimes be more flexible for dynamic memory allocation or algorithm implementations.

内容的提问来源于stack exchange，提问作者user3424522