/**
 * @param {number[][]} grid
 * @return {number}
 */
let minPathSum = function (grid) {
    let y = grid.length
    if (!y) {
        return 0
    }
    let x = grid[0].length

    let dp = []
    for (let i = 0; i < y; i++) {
        dp[i] = []
    }

    dp[0][0] = grid[0][0]
    
    // 第一行的基础状态 记得加上左边格子的值
    for (let j = 1; j < x; j++) {
        dp[0][j] = grid[0][j] + dp[0][j - 1]
    }

    // 第一列的基础状态 加上上方格子的最优解即可
    for (let i = 1; i < y; i++) {
        dp[i][0] = grid[i][0] + dp[i - 1][0]
    }

    // 开始求左上往右下求解
    for (let i = 1; i < grid.length; i++) {
        for (let j = 1; j < grid[i].length; j++) {
            let cur = grid[i][j]
            let fromUp = cur + (dp[i - 1][j] !== undefined ? dp[i - 1][j]: Infinity)
            let fromLeft = cur + (dp[i][j - 1] !== undefined ? dp[i][j - 1]: Infinity)

            dp[i][j] = Math.min(
                fromUp,
                fromLeft
            )
        }
    }
    return dp[y - 1][x - 1]
};