xiaoou33對既是素數又是回文的數特別感興趣。比如說151既是素數又是個回文。現在xiaoou333想要你幫助他找出某個范圍內的素數回文數，請你寫個程序找出 a 跟b 之間滿足條件的數。(5 <= a < b <= 100,000,000);?

Input

這里有許多組數據，每組包括兩組數據a跟b。

Output

對每一組數據,按從小到大輸出a，b之間所有滿足條件的素數回文數（包括a跟b）每組數據之后空一行。

Sample Input

5 500

Sample Output

5 7 11 101 131 151 181 191 313 353 373 383

// 判斷輸入的數是否為素數，若是，則將它轉為字符串判斷它是否為回文 1 #include<stdio.h> 2 #include<stdlib.h> 3 #include<string.h> 4 char num[100000001]; 5 int palindrome(char str[]) 6 { 7 int i, len, flag=1; 8 len=strlen(str); 9 for(i=0;i<len/2;i++) 10 if(str[i]!=str[len-1-i]) 11 { flag=0; break; } 12 return flag; 13 } 14 15 int prime(int n) 16 { 17 int i, flag=1; 18 for(i=2; i<n; i++) 19 if(n%i==0) 20 { flag=0; break; } 21 return flag; 22 } 23 24 int main() 25 { 26 int a, b, i; 27 while(scanf("%d %d", &a, &b)!=EOF) 28 { 29 for(i=a;i<=b;i++) 30 if(prime(i)) 31 { 32 itoa(i,num,10); 33 if(palindrome(num)) 34 puts(num); 35 } 36 printf("\n"); 37 } 38 return 0; 39 } Time Limit Exceeded // 縮短了判斷素數時遍歷的范圍 1 #include<stdio.h> 2 #include<stdlib.h> 3 #include<math.h> 4 #include<string.h> 5 char num[100000001]; 6 int palindrome(char str[]) 7 { 8 int i, len, flag=1; 9 len=strlen(str); 10 for(i=0;i<len/2;i++) 11 if(str[i]!=str[len-1-i]) 12 { flag=0; break; } 13 return flag; 14 } 15 16 int prime(int n) 17 { 18 int i, flag=1, k; 19 k=(int)ceil(sqrt(n*1.0)); 20 for(i=2; i<=k; i++) 21 if(n%i==0) 22 { flag=0; break; } 23 return flag; 24 } 25 26 int main() 27 { 28 int a, b, i; 29 while(scanf("%d %d", &a, &b)!=EOF) 30 { 31 for(i=a;i<=b;i++) 32 if(prime(i)) 33 { 34 itoa(i,num,10); 35 if(palindrome(num)) 36 puts(num); 37 } 38 printf("\n"); 39 } 40 return 0; 41 } Time Limit Exceeded*2 // 判整數型回文方法見代碼
// 判素數中的終止循環條件中無需調用sqrt 1 #include<stdio.h> 2 int palindrome(int x) 3 { 4 int i=x, j=0, flag=0; 5 while(i) 6 { j=j*10+i%10; i/=10; } 7 if(j==x) flag=1; 8 return flag; 9 } 10 11 int prime(int n) 12 { 13 int i, flag=1, k; 14 if(n!=2&&n%2==0) flag=0; 15 else 16 { 17 for(i=2; i*i<=n; i++) 18 if(n%i==0) 19 { flag=0; break; } 20 } 21 return flag; 22 } 23 24 int main() 25 { 26 int a, b, i; 27 while(scanf("%d %d", &a, &b)!=EOF) 28 { 29 for(i=a;i<=b;i++) 30 if(prime(i)) 31 if(palindrome(i)) 32 printf("%d\n", i); 33 printf("\n"); 34 } 35 return 0; 36 } Time Limit Exceeded*3 // 偶數除2外都不是素數
// 給定范圍內最大的素數回文為9989899.
// 除了11外，任意偶數長度的回文都是11的倍數 1 #include<stdio.h> 2 int palindrome(int x) 3 { 4 int i=x, j=0, flag=0; 5 while(i) 6 { j=j*10+i%10; i/=10; } 7 if(j==x) flag=1; 8 return flag; 9 } 10 11 int prime(int n) 12 { 13 int i, flag=1; 14 for(i=3; i*i<=n; i++) 15 if(n%i==0) 16 { flag=0; break; } 17 return flag; 18 } 19 20 int main() 21 { 22 int a, b, i; 23 while(scanf("%d %d", &a, &b)!=EOF) 24 { 25 for(i=a%2?a:a+1;i<=b&&i<=9989899;i+=2) 26 { 27 if(i>11&&i<100 || i>=1000&&i<10000 || i>=100000&&i<1000000) 28 continue; 29 if(prime(i)&&palindrome(i)) 30 printf("%d\n", i); 31 } 32 printf("\n"); 33 } 34 return 0; 35 } Time Limit Exceeded*4 // 打表。。。一次遍歷輸出 1 #include<stdio.h> 2 #include<process.h> 3 4 int palindrome(int x) 5 { 6 int i=x, j=0, flag=0; 7 while(i) 8 { j=j*10+i%10; i/=10; } 9 if(j==x) flag=1; 10 return flag; 11 } 12 13 int prime(int n) 14 { 15 int i, flag=1; 16 for(i=2; i*i<=n; i++) 17 if(n%i==0) 18 { flag=0; break; } 19 return flag; 20 } 21 22 int main() 23 { 24 FILE *fp; 25 if((fp=fopen("Ntest.txt","wt"))==NULL) 26 { 27 printf("Error!\n"); 28 exit(0); 29 } 30 int j=0; 31 for(int i=5;i<=100000000;i++) 32 if(prime(i)&&palindrome(i)) 33 { 34 j++; 35 if(j%5) fprintf(fp, "%d, ", i); 36 else fprintf(fp, "%d, \n", i); 37 } 38 fprintf(fp, "\n\n%d", j); 39 printf("Done!\n"); 40 fclose(fp); 41 return 0; 42 } 打表代碼 1 #include<stdio.h> 2 #define N 779 3 4 int table[N]= 5 { 6 5, 7, 11, 101, 131, 7 151, 181, 191, 313, 353, 8 373, 383, 727, 757, 787, 9 797, 919, 929, 10301, 10501, 10 10601, 11311, 11411, 12421, 12721, 11 12821, 13331, 13831, 13931, 14341, 12 14741, 15451, 15551, 16061, 16361, 13 16561, 16661, 17471, 17971, 18181, 14 18481, 19391, 19891, 19991, 30103, 15 30203, 30403, 30703, 30803, 31013, 16 31513, 32323, 32423, 33533, 34543, 17 34843, 35053, 35153, 35353, 35753, 18 36263, 36563, 37273, 37573, 38083, 19 38183, 38783, 39293, 70207, 70507, 20 70607, 71317, 71917, 72227, 72727, 21 73037, 73237, 73637, 74047, 74747, 22 75557, 76367, 76667, 77377, 77477, 23 77977, 78487, 78787, 78887, 79397, 24 79697, 79997, 90709, 91019, 93139, 25 93239, 93739, 94049, 94349, 94649, 26 94849, 94949, 95959, 96269, 96469, 27 96769, 97379, 97579, 97879, 98389, 28 98689, 1003001, 1008001, 1022201, 1028201, 29 1035301, 1043401, 1055501, 1062601, 1065601, 30 1074701, 1082801, 1085801, 1092901, 1093901, 31 1114111, 1117111, 1120211, 1123211, 1126211, 32 1129211, 1134311, 1145411, 1150511, 1153511, 33 1160611, 1163611, 1175711, 1177711, 1178711, 34 1180811, 1183811, 1186811, 1190911, 1193911, 35 1196911, 1201021, 1208021, 1212121, 1215121, 36 1218121, 1221221, 1235321, 1242421, 1243421, 37 1245421, 1250521, 1253521, 1257521, 1262621, 38 1268621, 1273721, 1276721, 1278721, 1280821, 39 1281821, 1286821, 1287821, 1300031, 1303031, 40 1311131, 1317131, 1327231, 1328231, 1333331, 41 1335331, 1338331, 1343431, 1360631, 1362631, 42 1363631, 1371731, 1374731, 1390931, 1407041, 43 1409041, 1411141, 1412141, 1422241, 1437341, 44 1444441, 1447441, 1452541, 1456541, 1461641, 45 1463641, 1464641, 1469641, 1486841, 1489841, 46 1490941, 1496941, 1508051, 1513151, 1520251, 47 1532351, 1535351, 1542451, 1548451, 1550551, 48 1551551, 1556551, 1557551, 1565651, 1572751, 49 1579751, 1580851, 1583851, 1589851, 1594951, 50 1597951, 1598951, 1600061, 1609061, 1611161, 51 1616161, 1628261, 1630361, 1633361, 1640461, 52 1643461, 1646461, 1654561, 1657561, 1658561, 53 1660661, 1670761, 1684861, 1685861, 1688861, 54 1695961, 1703071, 1707071, 1712171, 1714171, 55 1730371, 1734371, 1737371, 1748471, 1755571, 56 1761671, 1764671, 1777771, 1793971, 1802081, 57 1805081, 1820281, 1823281, 1824281, 1826281, 58 1829281, 1831381, 1832381, 1842481, 1851581, 59 1853581, 1856581, 1865681, 1876781, 1878781, 60 1879781, 1880881, 1881881, 1883881, 1884881, 61 1895981, 1903091, 1908091, 1909091, 1917191, 62 1924291, 1930391, 1936391, 1941491, 1951591, 63 1952591, 1957591, 1958591, 1963691, 1968691, 64 1969691, 1970791, 1976791, 1981891, 1982891, 65 1984891, 1987891, 1988891, 1993991, 1995991, 66 1998991, 3001003, 3002003, 3007003, 3016103, 67 3026203, 3064603, 3065603, 3072703, 3073703, 68 3075703, 3083803, 3089803, 3091903, 3095903, 69 3103013, 3106013, 3127213, 3135313, 3140413, 70 3155513, 3158513, 3160613, 3166613, 3181813, 71 3187813, 3193913, 3196913, 3198913, 3211123, 72 3212123, 3218123, 3222223, 3223223, 3228223, 73 3233323, 3236323, 3241423, 3245423, 3252523, 74 3256523, 3258523, 3260623, 3267623, 3272723, 75 3283823, 3285823, 3286823, 3288823, 3291923, 76 3293923, 3304033, 3305033, 3307033, 3310133, 77 3315133, 3319133, 3321233, 3329233, 3331333, 78 3337333, 3343433, 3353533, 3362633, 3364633, 79 3365633, 3368633, 3380833, 3391933, 3392933, 80 3400043, 3411143, 3417143, 3424243, 3425243, 81 3427243, 3439343, 3441443, 3443443, 3444443, 82 3447443, 3449443, 3452543, 3460643, 3466643, 83 3470743, 3479743, 3485843, 3487843, 3503053, 84 3515153, 3517153, 3528253, 3541453, 3553553, 85 3558553, 3563653, 3569653, 3586853, 3589853, 86 3590953, 3591953, 3594953, 3601063, 3607063, 87 3618163, 3621263, 3627263, 3635363, 3643463, 88 3646463, 3670763, 3673763, 3680863, 3689863, 89 3698963, 3708073, 3709073, 3716173, 3717173, 90 3721273, 3722273, 3728273, 3732373, 3743473, 91 3746473, 3762673, 3763673, 3765673, 3768673, 92 3769673, 3773773, 3774773, 3781873, 3784873, 93 3792973, 3793973, 3799973, 3804083, 3806083, 94 3812183, 3814183, 3826283, 3829283, 3836383, 95 3842483, 3853583, 3858583, 3863683, 3864683, 96 3867683, 3869683, 3871783, 3878783, 3893983, 97 3899983, 3913193, 3916193, 3918193, 3924293, 98 3927293, 3931393, 3938393, 3942493, 3946493, 99 3948493, 3964693, 3970793, 3983893, 3991993, 100 3994993, 3997993, 3998993, 7014107, 7035307, 101 7036307, 7041407, 7046407, 7057507, 7065607, 102 7069607, 7073707, 7079707, 7082807, 7084807, 103 7087807, 7093907, 7096907, 7100017, 7114117, 104 7115117, 7118117, 7129217, 7134317, 7136317, 105 7141417, 7145417, 7155517, 7156517, 7158517, 106 7159517, 7177717, 7190917, 7194917, 7215127, 107 7226227, 7246427, 7249427, 7250527, 7256527, 108 7257527, 7261627, 7267627, 7276727, 7278727, 109 7291927, 7300037, 7302037, 7310137, 7314137, 110 7324237, 7327237, 7347437, 7352537, 7354537, 111 7362637, 7365637, 7381837, 7388837, 7392937, 112 7401047, 7403047, 7409047, 7415147, 7434347, 113 7436347, 7439347, 7452547, 7461647, 7466647, 114 7472747, 7475747, 7485847, 7486847, 7489847, 115 7493947, 7507057, 7508057, 7518157, 7519157, 116 7521257, 7527257, 7540457, 7562657, 7564657, 117 7576757, 7586857, 7592957, 7594957, 7600067, 118 7611167, 7619167, 7622267, 7630367, 7632367, 119 7644467, 7654567, 7662667, 7665667, 7666667, 120 7668667, 7669667, 7674767, 7681867, 7690967, 121 7693967, 7696967, 7715177, 7718177, 7722277, 122 7729277, 7733377, 7742477, 7747477, 7750577, 123 7758577, 7764677, 7772777, 7774777, 7778777, 124 7782877, 7783877, 7791977, 7794977, 7807087, 125 7819187, 7820287, 7821287, 7831387, 7832387, 126 7838387, 7843487, 7850587, 7856587, 7865687, 127 7867687, 7868687, 7873787, 7884887, 7891987, 128 7897987, 7913197, 7916197, 7930397, 7933397, 129 7935397, 7938397, 7941497, 7943497, 7949497, 130 7957597, 7958597, 7960697, 7977797, 7984897, 131 7985897, 7987897, 7996997, 9002009, 9015109, 132 9024209, 9037309, 9042409, 9043409, 9045409, 133 9046409, 9049409, 9067609, 9073709, 9076709, 134 9078709, 9091909, 9095909, 9103019, 9109019, 135 9110119, 9127219, 9128219, 9136319, 9149419, 136 9169619, 9173719, 9174719, 9179719, 9185819, 137 9196919, 9199919, 9200029, 9209029, 9212129, 138 9217129, 9222229, 9223229, 9230329, 9231329, 139 9255529, 9269629, 9271729, 9277729, 9280829, 140 9286829, 9289829, 9318139, 9320239, 9324239, 141 9329239, 9332339, 9338339, 9351539, 9357539, 142 9375739, 9384839, 9397939, 9400049, 9414149, 143 9419149, 9433349, 9439349, 9440449, 9446449, 144 9451549, 9470749, 9477749, 9492949, 9493949, 145 9495949, 9504059, 9514159, 9526259, 9529259, 146 9547459, 9556559, 9558559, 9561659, 9577759, 147 9583859, 9585859, 9586859, 9601069, 9602069, 148 9604069, 9610169, 9620269, 9624269, 9626269, 149 9632369, 9634369, 9645469, 9650569, 9657569, 150 9670769, 9686869, 9700079, 9709079, 9711179, 151 9714179, 9724279, 9727279, 9732379, 9733379, 152 9743479, 9749479, 9752579, 9754579, 9758579, 153 9762679, 9770779, 9776779, 9779779, 9781879, 154 9782879, 9787879, 9788879, 9795979, 9801089, 155 9807089, 9809089, 9817189, 9818189, 9820289, 156 9822289, 9836389, 9837389, 9845489, 9852589, 157 9871789, 9888889, 9889889, 9896989, 9902099, 158 9907099, 9908099, 9916199, 9918199, 9919199, 159 9921299, 9923299, 9926299, 9927299, 9931399, 160 9932399, 9935399, 9938399, 9957599, 9965699, 161 9978799, 9980899, 9981899, 9989899 162 }; 163 164 int main() 165 { 166 int a, b, i; 167 while(scanf("%d %d", &a, &b)!=EOF) 168 { 169 for(i=0;i<N;i++) 170 if(table[i]>=a&&table[i]<=b) 171 printf("%d\n", table[i]); 172 printf("\n"); 173 } 174 return 0; 175 } AC

轉載于:https://www.cnblogs.com/goldenretriever/p/10356168.html

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