TheAlgorithms/Java · error · IndexOutOfBoundsException

Invalid column indices

Error message

Invalid column indices

What it means

Thrown by PrefixSum2D.sumRegion(row1, col1, row2, col2) when the column indices are invalid: col1 < 0, col2 >= number of columns, or col2 < col1. Checked only after row indices pass. Bounds are 0-based inclusive against the original matrix column count.

Source

Thrown at src/main/java/com/thealgorithms/prefixsum/PrefixSum2D.java:59

    }

    /**
     * Calculates the sum of the sub-matrix defined by (row1, col1) to (row2, col2).
     * Indices are 0-based.
     *
     * @param row1 Top row index.
     * @param col1 Left column index.
     * @param row2 Bottom row index.
     * @param col2 Right column index.
     * @return The sum of the sub-matrix.
     * @throws IndexOutOfBoundsException if indices are invalid.
     */
    public long sumRegion(int row1, int col1, int row2, int col2) {
        if (row1 < 0 || row2 >= prefixSums.length - 1 || row2 < row1) {
            throw new IndexOutOfBoundsException("Invalid row indices");
        }
        if (col1 < 0 || col2 >= prefixSums[0].length - 1 || col2 < col1) {
            throw new IndexOutOfBoundsException("Invalid column indices");
        }

        return prefixSums[row2 + 1][col2 + 1] - prefixSums[row1][col2 + 1] - prefixSums[row2 + 1][col1] + prefixSums[row1][col1];
    }
}

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Use inclusive 0-based indices: col2 should be lastColIndex (cols-1).
2. Normalize corners so col2 >= col1 (swap if inverted).
3. Convert 1-based external coordinates to 0-based before calling.

Example fix

// before
long s = ps2.sumRegion(r1, c1, r2, c2); // c2 may equal column count

// after
long s = ps2.sumRegion(r1, c1, r2, Math.min(c2, cols - 1));

int cols = matrix[0].length;
if (col1 < 0 || col2 >= cols || col2 < col1) {
    throw new IndexOutOfBoundsException("invalid column range");
}
long s = ps2.sumRegion(row1, col1, row2, col2);

static boolean validColRange(int c1, int c2Inclusive, int cols) {
    return c1 >= 0 && c2Inclusive < cols && c2Inclusive >= c1;
}

try {
    long s = ps2.sumRegion(r1, c1, r2, c2);
} catch (IndexOutOfBoundsException e) {
    logger.warn("Bad column range [{}, {}]", c1, c2);
}

When it happens

Trigger: Call sumRegion(0, -1, 2, 2), sumRegion(0, 0, 2, cols) (col2 past last column), or sumRegion(0, 3, 2, 1) (col2 < col1).

Common situations: Passing column count as right index (cols instead of cols-1); inverted width bounds; 1-based columns not converted.

Related errors

• Invalid row indices
• Invalid range indices
• Invalid range: [%d, %d] for array of size %d
• Input matrix cannot be null or empty
• Invalid range indices

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/0b44ffc912cdfa2f. Report an issue: GitHub.