[64] 最小路径和

/**
 * @param {number[][]} grid
 * @return {number}
 */
var minPathSum = function (grid) {
    const m = grid.length
    const n = grid[0].length
    for (let i = 1; i < n; i++) {
        grid[0][i] = grid[0][i] + grid[0][i - 1]
    }
    for (let j = 1; j < m; j++) {
        grid[j][0] = grid[j][0] + grid[j - 1][0]
    }
    for (let i = 1; i < m; i++) {
        for (let j = 1; j < n; j++) {
            grid[i][j] = grid[i][j] + Math.min(grid[i - 1][j], grid[i][j - 1])
        }
    }
    return grid[m - 1][n - 1]
};