【POJ】2739

Code

#include <cstdio>
using namespace std;

const int PRIME[]={0, 2, 5, 10, 17, 28, 41, 58, 77, 100, 129, 160, 197, 238, 281, 328, 381, 440, 501, 568, 639, 712, 791, 874, 963, 1060, 1161, 1264, 1371, 1480, 1593, 1720, 1851, 1988, 2127, 2276, 2427, 2584, 2747, 2914, 3087, 3266, 3447, 3638, 3831, 4028, 4227, 4438, 4661, 4888, 5117, 5350, 5589, 5830, 6081, 6338, 6601, 6870, 7141, 7418, 7699, 7982, 8275, 8582, 8893, 9206, 9523, 9854, 10191, 10538, 10887, 11240, 11599, 11966, 12339, 12718, 13101, 13490, 13887, 14288, 14697, 15116, 15537, 15968, 16401, 16840, 17283, 17732, 18189, 18650, 19113, 19580, 20059, 20546, 21037, 21536, 22039, 22548, 23069, 23592, 24133, 24680, 25237, 25800, 26369, 26940, 27517, 28104, 28697, 29296, 29897, 30504, 31117, 31734, 32353, 32984, 33625, 34268, 34915, 35568, 36227, 36888, 37561, 38238, 38921, 39612, 40313, 41022, 41741, 42468, 43201, 43940, 44683, 45434, 46191, 46952, 47721, 48494, 49281, 50078, 50887, 51698, 52519, 53342, 54169, 54998, 55837, 56690, 57547, 58406, 59269, 60146, 61027, 61910, 62797, 63704, 64615, 65534, 66463, 67400, 68341, 69288, 70241, 71208, 72179, 73156, 74139, 75130, 76127, 77136, 78149, 79168, 80189, 81220, 82253, 83292, 84341, 85392, 86453, 87516, 88585, 89672, 90763, 91856, 92953, 94056, 95165, 96282, 97405, 98534, 99685, 100838, 102001, 103172, 104353, 105540, 106733, 107934, 109147, 110364, 111587, 112816, 114047, 115284, 116533, 117792, 119069, 120348, 121631, 122920, 124211, 125508, 126809, 128112, 129419, 130738, 132059, 133386, 134747, 136114, 137487, 138868, 140267, 141676, 143099, 144526, 145955, 147388, 148827, 150274, 151725, 153178, 154637, 156108, 157589, 159072, 160559, 162048, 163541, 165040, 166551, 168074, 169605, 171148, 172697, 174250, 175809, 177376, 178947, 180526, 182109, 183706, 185307, 186914, 188523, 190136, 191755, 193376, 195003, 196640, 198297, 199960, 201627, 203296, 204989, 206686, 208385, 210094, 211815, 213538, 215271, 217012, 218759, 220512, 222271, 224048, 225831, 227618, 229407, 231208, 233019, 234842, 236673, 238520, 240381, 242248, 244119, 245992, 247869, 249748, 251637, 253538, 255445, 257358, 259289, 261222, 263171, 265122, 267095, 269074, 271061, 273054, 275051, 277050, 279053, 281064, 283081, 285108, 287137, 289176, 291229, 293292, 295361, 297442, 299525, 301612, 303701, 305800, 307911, 310024, 312153, 314284, 316421, 318562, 320705, 322858, 325019, 327198, 329401, 331608, 333821, 336042, 338279, 340518, 342761, 345012, 347279, 349548, 351821, 354102, 356389, 358682, 360979, 363288, 365599, 367932, 370271, 372612, 374959, 377310, 379667, 382038, 384415, 386796, 389179, 391568, 393961, 396360, 398771, 401188, 403611, 406048, 408489, 410936, 413395, 415862, 418335, 420812, 423315, 425836, 428367, 430906, 433449, 435998, 438549, 441106, 443685, 446276, 448869, 451478, 454095, 456716, 459349, 461996, 464653, 467312, 469975, 472646, 475323, 478006, 480693, 483382, 486075, 488774, 491481, 494192, 496905, 499624, 502353, 505084, 507825, 510574, 513327, 516094, 518871, 521660, 524451, 527248, 530049, 532852, 535671, 538504, 541341, 544184, 547035, 549892, 552753, 555632, 558519, 561416, 564319, 567228, 570145, 573072, 576011, 578964, 581921, 584884, 587853, 590824, 593823, 596824, 599835, 602854, 605877, 608914, 611955, 615004, 618065, 621132, 624211, 627294, 630383, 633492, 636611, 639732, 642869, 646032, 649199, 652368, 655549, 658736, 661927, 665130, 668339, 671556, 674777, 678006, 681257, 684510, 687767, 691026, 694297, 697596, 700897, 704204, 707517, 710836, 714159, 717488, 720819, 724162, 727509, 730868, 734229, 737600, 740973, 744362, 747753, 751160, 754573, 758006, 761455, 764912, 768373, 771836, 775303, 778772, 782263, 785762, 789273, 792790, 796317, 799846, 803379, 806918, 810459, 814006, 817563, 821122, 824693, 828274, 831857, 835450, 839057, 842670, 846287, 849910, 853541, 857178, 860821, 864480, 868151, 871824, 875501, 879192, 882889, 886590, 890299, 894018, 897745, 901478, 905217, 908978, 912745, 916514, 920293, 924086, 927883, 931686, 935507, 939330, 943163, 947010, 950861, 954714, 958577, 962454, 966335, 970224, 974131, 978042, 981959, 985878, 989801, 993730, 997661, 1001604, 1005551, 1009518, 1013507, 1017508, 1021511, 1025518, 1029531, 1033550, 1037571, 1041598, 1045647, 1049698, 1053755, 1057828, 1061907, 1065998, 1070091, 1074190, 1078301, 1082428, 1086557, 1090690, 1094829, 1098982, 1103139, 1107298, 1111475, 1115676, 1119887, 1124104, 1128323, 1132552, 1136783, 1141024, 1145267, 1149520, 1153779, 1158040, 1162311, 1166584, 1170867, 1175156, 1179453, 1183780, 1188117, 1192456, 1196805, 1201162, 1205525, 1209898, 1214289, 1218686, 1223095, 1227516, 1231939, 1236380, 1240827, 1245278, 1249735, 1254198, 1258679, 1263162, 1267655, 1272162, 1276675, 1281192, 1285711, 1290234, 1294781, 1299330, 1303891, 1308458, 1313041, 1317632, 1322229, 1326832, 1331453, 1336090, 1340729, 1345372, 1350021, 1354672, 1359329, 1363992, 1368665, 1373344, 1378035, 1382738, 1387459, 1392182, 1396911, 1401644, 1406395, 1411154, 1415937, 1420724, 1425513, 1430306, 1435105, 1439906, 1444719, 1449536, 1454367, 1459228, 1464099, 1468976, 1473865, 1478768, 1483677, 1488596, 1493527, 1498460, 1503397, 1508340, 1513291, 1518248, 1523215, 1528184, 1533157, 1538144, 1543137, 1548136, 1553139, 1558148, 1563159, 1568180, 1573203, 1578242, 1583293, 1588352, 1593429, 1598510, 1603597, 1608696, 1613797, 1618904, 1624017, 1629136, 1634283, 1639436, 1644603, 1649774, 1654953, 1660142, 1665339, 1670548, 1675775, 1681006, 1686239, 1691476, 1696737, 1702010, 1707289, 1712570, 1717867, 1723170, 1728479, 1733802, 1739135, 1744482, 1749833, 1755214, 1760601, 1765994, 1771393, 1776800, 1782213, 1787630, 1793049, 1798480, 1803917, 1809358, 1814801, 1820250, 1825721, 1831198, 1836677, 1842160, 1847661, 1853164, 1858671, 1864190, 1869711, 1875238, 1880769, 1886326, 1891889, 1897458, 1903031, 1908612, 1914203, 1919826, 1925465, 1931106, 1936753, 1942404, 1948057, 1953714, 1959373, 1965042, 1970725, 1976414, 1982107, 1987808, 1993519, 1999236, 2004973, 2010714, 2016457, 2022206, 2027985, 2033768, 2039559, 2045360, 2051167, 2056980, 2062801, 2068628, 2074467, 2080310, 2086159, 2092010, 2097867, 2103728, 2109595, 2115464, 2121343, 2127224, 2133121, 2139024, 2144947, 2150874, 2156813, 2162766, 2168747, 2174734, 2180741, 2186752, 2192781, 2198818, 2204861, 2210908, 2216961, 2223028, 2229101, 2235180, 2241269, 2247360, 2253461, 2259574, 2265695, 2271826, 2277959, 2284102, 2290253, 2296416, 2302589, 2308786, 2314985, 2321188, 2327399, 2333616, 2339837, 2346066, 2352313, 2358570, 2364833, 2371102, 2377373, 2383650, 2389937, 2396236, 2402537, 2408848, 2415165, 2421488, 2427817, 2434154, 2440497, 2446850, 2453209, 2459570, 2465937, 2472310, 2478689, 2485078, 2491475, 2497896, 2504323, 2510772, 2517223, 2523692, 2530165, 2536646, 2543137, 2549658, 2556187, 2562734, 2569285, 2575838, 2582401, 2588970, 2595541, 2602118, 2608699, 2615298, 2621905, 2628524, 2635161, 2641814, 2648473, 2655134, 2661807, 2668486, 2675175, 2681866, 2688567, 2695270, 2701979, 2708698, 2715431, 2722168, 2728929, 2735692, 2742471, 2749252, 2756043, 2762836, 2769639, 2776462, 2783289, 2790118, 2796951, 2803792, 2810649, 2817512, 2824381, 2831252, 2838135, 2845034, 2851941, 2858852, 2865769, 2872716, 2879665, 2886624, 2893585, 2900552, 2907523, 2914500, 2921483, 2928474, 2935471, 2942472, 2949485, 2956504, 2963531, 2970570, 2977613, 2984670, 2991739, 2998818, 3005921, 3013030, 3020151, 3027278, 3034407, 3041558, 3048717, 3055894, 3063081, 3070274, 3077481, 3084692, 3091905, 3099124, 3106353, 3113590, 3120833, 3128080, 3135333, 3142616, 3149913, 3157220, 3164529, 3171850, 3179181, 3186514, 3193863, 3201214, 3208583, 3215976, 3223387, 3230804, 3238237, 3245688, 3253145, 3260604, 3268081, 3275562, 3283049, 3290538, 3298037, 3305544, 3313061, 3320584, 3328113, 3335650, 3343191, 3350738, 3358287, 3365846, 3373407, 3380980, 3388557, 3396140, 3403729, 3411320, 3418923, 3426530, 3434151, 3441790, 3449433, 3457082, 3464751, 3472424, 3480105, 3487792, 3495483, 3503182, 3510885, 3518602, 3526325, 3534052, 3541793, 3549546, 3557303, 3565062, 3572851, 3580644, 3588461, 3596284, 3604113, 3611954, 3619807, 3627674, 3635547, 3643424, 3651303, 3659186, 3667087, 3674994, 3682913, 3690840, 3698773, 3706710, 3714659, 3722610, 3730573, 3738566, 3746575, 3754586, 3762603, 3770642, 3778695, 3786754, 3794823, 3802904, 3810991, 3819080, 3827173, 3835274, 3843385, 3851502, 3859625, 3867772, 3875933, 3884100, 3892271, 3900450, 3908641, 3916850, 3925069, 3933290, 3941521, 3949754, 3957991, 3966234, 3974497, 3982766, 3991039, 3999326, 4007617, 4015910, 4024207, 4032518, 4040835, 4049164, 4057517, 4065880, 4074249, 4082626, 4091013, 4099402, 4107821, 4116244, 4124673, 4133104, 4141547, 4149994, 4158455, 4166922, 4175423, 4183936, 4192457, 4200984, 4209521, 4218060, 4226603, 4235166, 4243739, 4252320, 4260917, 4269516, 4278125, 4286748, 4295375, 4304004, 4312645, 4321292, 4329955, 4338624, 4347301, 4355982, 4364671, 4373364, 4382063, 4390770, 4399483, 4408202, 4416933, 4425670, 4434411, 4443158, 4451911, 4460672, 4469451, 4478234, 4487037, 4495844, 4504663, 4513484, 4522315, 4531152, 4539991, 4548840, 4557701, 4566564, 4575431, 4584318, 4593211, 4602134, 4611063, 4619996, 4628937, 4637888, 4646851, 4655820, 4664791, 4673790, 4682791, 4691798, 4700809, 4709822, 4718851, 4727892, 4736935, 4745984, 4755043, 4764110, 4773201, 4782304, 4791413, 4800540, 4809673, 4818810, 4827961, 4837118, 4846279, 4855452, 4864633, 4873820, 4883019, 4892222, 4901431, 4910652, 4919879, 4929118, 4938359, 4947616, 4956893, 4966174, 4975457, 4984750, 4994061, 5003380, 5012703, 5022040, 5031381, 5040724, 5050073, 5059444, 5068821, 5078212, 5087609, 5097012, 5106425, 5115844, 5125265, 5134696, 5144129, 5153566, 5163005, 5172466, 5181929, 5191396, 5200869, 5210348, 5219839, 5229336, 5238847, 5248368, 5257901, 5267440, 5276987, 5286538, 5296125, 5305726, 5315339, 5324958, 5334581, 5344210, 5353841, 5363484, 5373133, 5382794, 5392471, 5402150, 5411839, 5421536, 5431255, 5440976, 5450709, 5460448, 5470191, 5479940, 5489707, 5499476, 5509257, 5519044, 5528835, 5538638, 5548449, 5558266, 5568095, 5577928, 5587767, 5597618, 5607475, 5617334, 5627205, 5637088, 5646975, 5656876, 5666783, 5676706, 5686635, 5696566, 5706507, 5716456, 5726423, 5736396, 5746403, 5756412, 5766449, 5776488, 5786549, 5796616, 5806685, 5816764};
int t, ans;

inline int getSum(int l, int r){return PRIME[r] - PRIME[l - 1];}

inline int calc(int x){
    int lcur = 1;
    int rcur = 1;
    int ret = 0;
    while(getSum(lcur, lcur) <= x){
        int s = getSum(lcur, rcur);
        // printf("getSum(%d, %d) = %d
", lcur, rcur, s);
        if (s == x){
            ret++;
            lcur++;
            rcur = lcur;
            continue;
        }
        if (s > x){
            lcur++;
            rcur = lcur;
            continue;
        }
        rcur++;
    }
    return ret;
}

int main(int argc, char const *argv[]){
    while(scanf("%d", &t) && t){
        ans = calc(t);
        printf("%d
", ans);
    }
    return 0;
}

---

Review

• 近期做得最顺畅的水题（大约是因为题意明确吧）。
• 尺取法，或者说滑动窗口的思想。
• 先写个程序打出素数表前缀和。初始化不必指定数组元素个数。
• 最好做法：把数据范围内的所有答案先算出来，然后O（1）过。