119. 杨辉三角 II #

/**
 * @param {number} rowIndex
 * @return {number[]}
 */
// 解法一 暴力枚举
var getRow = function (rowIndex) {
  var map = [
    [1],
    [1, 1],
    [1, 2, 1],
    [1, 3, 3, 1],
    [1, 4, 6, 4, 1],
    [1, 5, 10, 10, 5, 1],
    [1, 6, 15, 20, 15, 6, 1],
    [1, 7, 21, 35, 35, 21, 7, 1],
    [1, 8, 28, 56, 70, 56, 28, 8, 1],
    [1, 9, 36, 84, 126, 126, 84, 36, 9, 1],
    [1, 10, 45, 120, 210, 252, 210, 120, 45, 10, 1],
    [1, 11, 55, 165, 330, 462, 462, 330, 165, 55, 11, 1],
    [1, 12, 66, 220, 495, 792, 924, 792, 495, 220, 66, 12, 1],
    [1, 13, 78, 286, 715, 1287, 1716, 1716, 1287, 715, 286, 78, 13, 1],
    [1, 14, 91, 364, 1001, 2002, 3003, 3432, 3003, 2002, 1001, 364, 91, 14, 1],
    [
      1, 15, 105, 455, 1365, 3003, 5005, 6435, 6435, 5005, 3003, 1365, 455, 105,
      15, 1,
    ],
    [
      1, 16, 120, 560, 1820, 4368, 8008, 11440, 12870, 11440, 8008, 4368, 1820,
      560, 120, 16, 1,
    ],
    [
      1, 17, 136, 680, 2380, 6188, 12376, 19448, 24310, 24310, 19448, 12376,
      6188, 2380, 680, 136, 17, 1,
    ],
    [
      1, 18, 153, 816, 3060, 8568, 18564, 31824, 43758, 48620, 43758, 31824,
      18564, 8568, 3060, 816, 153, 18, 1,
    ],
    [
      1, 19, 171, 969, 3876, 11628, 27132, 50388, 75582, 92378, 92378, 75582,
      50388, 27132, 11628, 3876, 969, 171, 19, 1,
    ],
    [
      1, 20, 190, 1140, 4845, 15504, 38760, 77520, 125970, 167960, 184756,
      167960, 125970, 77520, 38760, 15504, 4845, 1140, 190, 20, 1,
    ],
    [
      1, 21, 210, 1330, 5985, 20349, 54264, 116280, 203490, 293930, 352716,
      352716, 293930, 203490, 116280, 54264, 20349, 5985, 1330, 210, 21, 1,
    ],
    [
      1, 22, 231, 1540, 7315, 26334, 74613, 170544, 319770, 497420, 646646,
      705432, 646646, 497420, 319770, 170544, 74613, 26334, 7315, 1540, 231, 22,
      1,
    ],
    [
      1, 23, 253, 1771, 8855, 33649, 100947, 245157, 490314, 817190, 1144066,
      1352078, 1352078, 1144066, 817190, 490314, 245157, 100947, 33649, 8855,
      1771, 253, 23, 1,
    ],
    [
      1, 24, 276, 2024, 10626, 42504, 134596, 346104, 735471, 1307504, 1961256,
      2496144, 2704156, 2496144, 1961256, 1307504, 735471, 346104, 134596,
      42504, 10626, 2024, 276, 24, 1,
    ],
    [
      1, 25, 300, 2300, 12650, 53130, 177100, 480700, 1081575, 2042975, 3268760,
      4457400, 5200300, 5200300, 4457400, 3268760, 2042975, 1081575, 480700,
      177100, 53130, 12650, 2300, 300, 25, 1,
    ],
    [
      1, 26, 325, 2600, 14950, 65780, 230230, 657800, 1562275, 3124550, 5311735,
      7726160, 9657700, 10400600, 9657700, 7726160, 5311735, 3124550, 1562275,
      657800, 230230, 65780, 14950, 2600, 325, 26, 1,
    ],
    [
      1, 27, 351, 2925, 17550, 80730, 296010, 888030, 2220075, 4686825, 8436285,
      13037895, 17383860, 20058300, 20058300, 17383860, 13037895, 8436285,
      4686825, 2220075, 888030, 296010, 80730, 17550, 2925, 351, 27, 1,
    ],
    [
      1, 28, 378, 3276, 20475, 98280, 376740, 1184040, 3108105, 6906900,
      13123110, 21474180, 30421755, 37442160, 40116600, 37442160, 30421755,
      21474180, 13123110, 6906900, 3108105, 1184040, 376740, 98280, 20475, 3276,
      378, 28, 1,
    ],
    [
      1, 29, 406, 3654, 23751, 118755, 475020, 1560780, 4292145, 10015005,
      20030010, 34597290, 51895935, 67863915, 77558760, 77558760, 67863915,
      51895935, 34597290, 20030010, 10015005, 4292145, 1560780, 475020, 118755,
      23751, 3654, 406, 29, 1,
    ],
    [
      1, 30, 435, 4060, 27405, 142506, 593775, 2035800, 5852925, 14307150,
      30045015, 54627300, 86493225, 119759850, 145422675, 155117520, 145422675,
      119759850, 86493225, 54627300, 30045015, 14307150, 5852925, 2035800,
      593775, 142506, 27405, 4060, 435, 30, 1,
    ],
    [
      1, 31, 465, 4495, 31465, 169911, 736281, 2629575, 7888725, 20160075,
      44352165, 84672315, 141120525, 206253075, 265182525, 300540195, 300540195,
      265182525, 206253075, 141120525, 84672315, 44352165, 20160075, 7888725,
      2629575, 736281, 169911, 31465, 4495, 465, 31, 1,
    ],
    [
      1, 32, 496, 4960, 35960, 201376, 906192, 3365856, 10518300, 28048800,
      64512240, 129024480, 225792840, 347373600, 471435600, 565722720,
      601080390, 565722720, 471435600, 347373600, 225792840, 129024480,
      64512240, 28048800, 10518300, 3365856, 906192, 201376, 35960, 4960, 496,
      32, 1,
    ],
    [
      1, 33, 528, 5456, 40920, 237336, 1107568, 4272048, 13884156, 38567100,
      92561040, 193536720, 354817320, 573166440, 818809200, 1037158320,
      1166803110, 1166803110, 1037158320, 818809200, 573166440, 354817320,
      193536720, 92561040, 38567100, 13884156, 4272048, 1107568, 237336, 40920,
      5456, 528, 33, 1,
    ],
  ]
  return map[rowIndex]
}

// 解法二 使用对应行公式 第(i+1)项是第i项的倍数=(n-i)/(i+1);
var getRow = function (rowIndex) {
  var cur = 1,
    res = []
  for (let i = 0; i <= rowIndex; i++) {
    res.push(cur)
    cur = (cur * (rowIndex - i)) / (i + 1)
  }
  return res
}

console.log(getRow(0))
console.log(getRow(1))
console.log(getRow(3))