62. 不同路径

递归

/**
 * @param {number} m
 * @param {number} n
 * @return {number}
 */
var uniquePaths = function (m, n) {
  const cache = {}
  const dp = (i, j) => {
    if (i === 0 || j === 0) {
      return 1
    }
    const key = `${i}-${j}`
    if (cache[key]) {
      return cache[key]
    }
    return (cache[key] = dp(i - 1, j) + dp(i, j - 1))
  }
  return dp(m - 1, n - 1)
}

循环