447-easy-Number_of_Boomerangs.js

/**
447. Number of Boomerangs

Given n points in the plane that are all pairwise distinct, a "boomerang" is a tuple of points (i, j, k) such that the distance between i and j equals the distance between i and k (the order of the tuple matters).

Find the number of boomerangs. You may assume that n will be at most 500 and coordinates of points are all in the range [-10000, 10000] (inclusive).

Example:
Input:
[[0,0],[1,0],[2,0]]

Output:
2

Explanation:
The two boomerangs are [[1,0],[0,0],[2,0]] and [[1,0],[2,0],[0,0]]
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 */

/**
 * @param {number[][]} points
 * @return {number}
 */
var numberOfBoomerangs = function (points) {
  if (points.length <= 2) {
    return 0;
  }

  var total = 0;

  for (var i = 0; i < points.length; i++) {

    // 记录从当前这个点到其他所有点的距离出现了几种长度并记录每种距离出现的次数
    var currentPointDistances = {};

    for (var j = 0; j < points.length; j++) {
      if (i !== j) {

        var distance = calcDistance(points[i][0], points[i][1], points[j][0], points[j][1]);

        if (currentPointDistances.hasOwnProperty(distance)) {
          currentPointDistances[distance]++;
        } else {
          currentPointDistances[distance] = 1;
        }

      }
    }

    var currentPointDistancesKeys = Object.keys(currentPointDistances);

    for (var j = 0; j < currentPointDistancesKeys.length; j++) {
      // 如果某种距离出现的次数超过了两次，则统计次数
      if (currentPointDistances[currentPointDistancesKeys[j]] >= 2) {
        total += currentPointDistances[currentPointDistancesKeys[j]] * (currentPointDistances[currentPointDistancesKeys[j]] - 1);
      }
    }
  }

  function calcDistance(x1, y1, x2, y2) {
    return (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  }

  return total;
};

numberOfBoomerangs([[3327, -549], [9196, -8118], [7610, -9506], [5098, 8392], [8582, 7953], [1053, 5802], [3847, 2652], [7654, 8355], [1614, -9409], [9986, 5538], [4660, 2944], [4528, -9512], [7483, -1455], [3422, -3966], [2037, -4456], [5107, -4635], [4996, 655], [7247, 2606], [1149, 8697], [7350, 6083], [3002, 8403], [8238, 6850], [1055, 5892], [5205, 9021], [2835, 5191], [911, -2505], [4488, -4561], [7983, -1677], [336, -2243], [4358, -1274], [3302, 9465], [4091, -5350], [120, 7690], [3608, 7622], [6388, -9042], [57, -610], [9361, 8295], [6240, -3232], [540, 7797], [2141, -6625], [9341, 3053], [7223, 3829], [4844, 1558], [2152, -8467], [9316, 6510], [259, -1030], [2327, -5650], [9972, 8800], [2040, -6420], [2774, 4780], [4538, -7169], [4171, -6101], [7479, -3237], [7019, -1981], [4561, -4488], [7746, 254], [4917, 4969], [4083, -238], [6528, -7413], [1295, -7804], [5450, -8446], [1166, -5871], [2256, -8862], [2929, -5704], [4718, 2055], [5429, -4392], [4887, 9600], [9507, -1282], [2715, 2878], [6737, -6372], [8390, -9165], [3882, 3308], [5805, 4317], [9422, 8685], [3257, -2931], [881, -1293], [8623, -1601], [2836, 879], [5889, 2118], [1527, 607], [4173, -3044], [6215, 5412], [2908, -7926], [4130, -8024], [1304, 7219], [1956, -3954], [8055, 5839], [5706, 212], [6508, 5128], [8897, 9765], [2197, -3870], [8472, -2828], [4529, 7661], [4403, -9582], [6131, -7717], [7377, -3344], [5591, 9944], [2069, -5148], [8370, -7449], [6828, -3974], [6123, -1216], [2072, 530], [975, -2221], [7094, -2516], [9259, -4009], [7249, 7809], [8473, 2074], [4981, -6998], [9735, 5737], [9772, 5866], [8020, -6499], [8874, -6389], [3445, -9057], [4815, 8167], [9847, 1643], [4193, 2322], [6780, 2617], [9204, 4107], [396, 6298], [1591, 6008], [2289, -4807], [3817, 762], [7267, 5150], [116, -6646], [887, -3760], [5572, -4741], [9741, 4446], [5223, -462], [1742, 38], [7705, 1589], [1682, -1750], [263, 4814], [867, 9467], [8921, 7616], [5765, -3135], [3624, 4406], [2058, -2559], [1520, -675], [2591, -2012], [2679, -169], [4228, -1749], [5090, -6031], [2697, -9687], [9859, 791], [352, 3916], [8732, -1614], [2166, 8995], [3200, 9385], [4814, -1527], [7001, 579], [5338, -3023], [1337, -2604], [4418, -7143], [3073, 3362], [845, -7896], [3193, -8575], [6707, 4635], [1746, -595], [4949, 1605], [6548, -8347], [1873, 5281], [39, -5961], [4276, -409], [9777, -909], [8064, 3130], [6022, -245], [108, 7360], [7151, 4526], [6569, -3423], [4240, -2585], [8681, -2567], [5192, 5389], [2069, -3061], [1146, 3370], [4896, 7694], [5023, 6770], [2975, -8586], [7161, -6396], [1005, 6938], [2695, -4579], [69, -4931], [5176, 177], [2429, -1320], [1055, 8999], [5257, -4704], [2766, -6062], [9081, -2042], [5679, -2498], [1249, 6825], [7224, -3854], [872, 2247], [2916, -6153], [3661, -9923], [7451, -8982], [7016, 6498], [6440, -6563], [1568, -8384], [9966, -9651], [296, 1021], [9348, -8095], [2669, 8466], [2196, -8249], [2777, 7875], [5605, 4026], [1053, -7170], [172, -8075], [1429, -6912], [5772, -8557], [9518, -424], [2461, 2886], [2426, -1099], [6323, -6006], [6870, -3711], [696, 3518], [3662, 6396], [5424, -3668], [4863, 7620], [4435, 7640], [1847, -3608], [8018, -7100], [9222, -5457], [4825, 7004], [3983, -3050], [8447, -6499], [2878, -9092], [6387, 5304], [6162, -938], [5651, 3032], [5351, 6347], [2902, -4634], [2743, 8326], [8050, -6042], [2298, -1163], [7950, -9502], [5229, -4031], [3398, -9196], [512, -5424], [7808, 847], [7878, 6255], [4349, 7108], [7163, 736], [8764, 9677], [6151, -5585], [2709, -2146], [7114, 5612], [3220, -3790], [290, -8730], [168, 8941], [107, -5529], [9439, -8311], [440, 9189], [2493, 7304], [117, 6653], [8151, -5653], [2908, 8852], [1455, -3577], [5941, -3428], [6101, -7908], [7339, 5162], [9946, -5546], [7126, 9519], [7016, 3769], [789, 7184], [2710, -2751], [1655, -1499], [5290, -1553], [4042, -2217], [2103, -9488], [788, -3393], [1211, 3696], [1811, 9019], [6471, -2248], [5591, 8924], [6196, 2930], [4087, 6143], [3736, 7565], [5662, -9248], [1334, 2803], [4289, -9604], [6404, 2296], [8897, -8306], [7096, -708], [5829, 9199], [6156, -3383], [2158, -2633], [6665, -9678], [6386, 3137], [8074, 1977], [2061, 4271], [4908, -7500], [6766, 4996], [66, 8780], [5749, 1400], [7935, 38], [1797, -5660], [2334, 7046], [2386, 9430], [2690, -1784], [4982, -1154], [1185, 3492], [6214, -2149], [3814, 8952], [7340, 8241], [930, -4247], [8864, 2190], [8254, 5630], [7186, -5328], [762, 9287], [6072, 8697], [9325, -5779], [9389, 1660], [7620, -8224], [7442, -9690], [9992, -7576], [5509, 7529], [2269, 8075], [5380, -3917], [7027, -7280], [4324, -5691], [8474, 3188], [6499, 3080], [5170, -9962], [7752, 5932], [9325, 176], [982, -1349], [4398, 371], [6663, -1630], [2147, -9543], [5032, 8491], [9234, 541], [6021, 1503], [8616, 7753], [3938, -8004], [6826, 8263], [6305, -8348], [7803, 9157], [4732, -674], [9195, -1164], [5258, 8520], [9012, 2592], [3523, -238], [2964, 6538], [8132, 1463], [3348, -6835], [6307, 2582], [58, -7672], [437, 5027], [6433, 4375], [7023, 3259], [8990, -6672], [4911, 3146], [2485, -4005], [2472, 8032], [4831, -5918], [2905, 196], [6675, 6428], [9958, 9639], [9319, 4443], [7454, -7333], [3960, 3761], [1601, -9630], [2441, 2038], [5397, -1125], [6413, 2420], [8486, 1756], [2101, 3398], [4902, 938], [5745, -2626], [5323, -3071], [1456, 8228], [7125, -1869], [1008, 3435], [4122, 6679], [4230, 1577], [9346, 8190], [1690, 947], [4913, 4132], [9337, 310], [3007, -4249], [9083, -8507], [7507, -2464], [1243, -7591], [4826, -3011], [6135, -9851], [3918, 7591], [8377, -2605], [5723, -4262], [830, -3803], [2417, -8587], [7774, 8116], [5955, 9465], [5415, 868], [9949, -5247], [1179, 2956], [6856, 6614], [801, -9285], [4150, 8397], [9476, 8976], [1738, -4389], [9126, 2008], [3202, 3855], [9403, -4723], [9593, 6585], [1475, -7989], [7998, -4399], [127, 306], [1418, -4458], [1174, 1367], [6647, -7647], [4323, 3503], [8967, 1477], [4218, 9469], [6226, 3694], [8446, -2036], [9305, 3924], [9972, 8860], [7779, 5727], [4137, -6275], [8664, 1964], [5736, -6985], [7566, -7785], [3321, 8984], [4109, 4495], [352, 757], [3201, 1027], [4260, -1480], [8856, 4831], [7990, -4918], [8525, -7212], [3046, -5817], [6712, -630], [3043, -5509], [1449, -6468], [8216, -3534], [5497, 304], [9481, 3063], [8871, 9154], [8399, 2981], [1, 8751], [90, -6798], [6131, -9298], [8075, -5013], [5533, 6065], [70, -9589], [5205, 9468], [946, 1917], [5191, -6011], [2760, -7008], [3873, 7329], [9458, 9370], [7633, 5291], [8785, 2857], [797, 3537], [2190, -9201], [2288, -7720], [353, 4771], [9334, -1572], [9759, 1220], [845, -3819], [7983, 6050], [2001, -1071], [4319, -2808], [9270, 7080], [6537, 3143], [4409, 2347], [8866, 8394], [7639, 4003], [7603, 4788], [7540, -207], [5587, 6181], [8425, 5941], [952, -5888], [721, -2937], [5332, -8433], [3244, -6685], [3969, 5246], [2244, 8289], [8790, -8486], [1721, -4673], [1009, -3870], [7675, 9875], [876, -8334], [231, -1520], [6454, 7771], [4625, 2042], [304, 9403], [4335, -8743], [3515, -4944], [4672, 8847], [2975, 7917], [8514, 6945], [3163, 758], [1586, 1953], [8624, -6693], [7281, 9633], [5789, 1308], [5861, -6983], [2974, -3908], [7849, -572], [215, -7525]]);