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export default interface NumMatrix {    sumRegion(row1: number, col1: number, row2: number, col2: number): number;}
export default function NumMatrix(matrix: number[][]): NumMatrix {    const m = matrix.length;    const n = matrix[0].length;    const sums: number[][] = Array.from({ length: m + 1 }).map(() =>        Array(n + 1).fill(0)    );    matrix.forEach((a, i) =>        a.forEach((v, j) => {            sums[i + 1][j + 1] = sums[i][j + 1] + sums[i + 1][j] - sums[i][j] +                v;        })    );    return {        sumRegion(            row1: number,            col1: number,            row2: number,            col2: number,        ): number {            return (                sums[row2 + 1][col2 + 1] -                sums[row1][col2 + 1] -                sums[row2 + 1][col1] +                sums[row1][col1]            );        },    };}