http://acm.zzuli.edu.cn/problem.php?id=2211Click to open the link
Topic description
Xiaoming likes palindromic numbers very much. He found that some palindrome numbers are very interesting. They are not only palindrome numbers, but also prime numbers, so Xiaoming turns them into interesting strings. Now he wants to know the number of interesting palindrome numbers between any two integers, can you help him smart?
enter
The first line enters an integer T, representing the number of instances. (T < 10000)
Next T lines, each line input two integers a, b. (0 <= a <= b <= 10000000)
output
The output has T lines, and each line outputs an integer representing the number of interesting palindromes in the interval [a, b].
sample input
2
2 5
10 20
Sample output
3
1
If you judge one by one, it will definitely time out, the number is not too many, first make a table to calculate all the numbers that meet the requirements, and finally judge.
By meter:
#include<stdio.h>
#include<math.h>
#define N 10000000
int a[N];
int HW (int n)
{
int len, i, s;
len = log10 (n);
while(n)
{
s = pow (10, len);
if(n%10!=n/s)
return 0;
else{
n=n%s;
n/=10;
len- = 2;
}
}
return 1;
}
intmain()
{
int i,j,sum=0;
a[0]=a[1]=1;
for(i=2;i<N/2;i++)
{
if(a[i]==0)
for(j=2*i;j<N;j+=i)
{
a[j]=1;
}
}
for(i=2;i<N;i++)
{
if(a[i]==0)
{
if(HW(i))
{
printf("%d,",i);
sum++;
if(sum%10==0)
printf("\n");
}
}
}
printf("%d",sum);
}
AC code:
#include<stdio.h>
int f[800]={2,3,5,7,11,101,131,151,181,191,
313,353,373,383,727,757,787,797,919,929,
10301,10501,10601,11311,11411,12421,12721,12821,13331,13831,
13931,14341,14741,15451,15551,16061,16361,16561,16661,17471,
17971,18181,18481,19391,19891,19991,30103,30203,30403,30703,
30803,31013,31513,32323,32423,33533,34543,34843,35053,35153,
35353,35753,36263,36563,37273,37573,38083,38183,38783,39293,
70207,70507,70607,71317,71917,72227,72727,73037,73237,73637,
74047,74747,75557,76367,76667,77377,77477,77977,78487,78787,
78887,79397,79697,79997,90709,91019,93139,93239,93739,94049,
94349,94649,94849,94949,95959,96269,96469,96769,97379,97579,
97879,98389,98689,1003001,1008001,1022201,1028201,1035301,1043401,1055501,
1062601,1065601,1074701,1082801,1085801,1092901,1093901,1114111,1117111,1120211,
1123211,1126211,1129211,1134311,1145411,1150511,1153511,1160611,1163611,1175711,
1177711,1178711,1180811,1183811,1186811,1190911,1193911,1196911,1201021,1208021,
1212121,1215121,1218121,1221221,1235321,1242421,1243421,1245421,1250521,1253521,
1257521,1262621,1268621,1273721,1276721,1278721,1280821,1281821,1286821,1287821,
1300031,1303031,1311131,1317131,1327231,1328231,1333331,1335331,1338331,1343431,
1360631,1362631,1363631,1371731,1374731,1390931,1407041,1409041,1411141,1412141,
1422241,1437341,1444441,1447441,1452541,1456541,1461641,1463641,1464641,1469641,
1486841,1489841,1490941,1496941,1508051,1513151,1520251,1532351,1535351,1542451,
1548451,1550551,1551551,1556551,1557551,1565651,1572751,1579751,1580851,1583851,
1589851,1594951,1597951,1598951,1600061,1609061,1611161,1616161,1628261,1630361,
1633361,1640461,1643461,1646461,1654561,1657561,1658561,1660661,1670761,1684861,
1685861,1688861,1695961,1703071,1707071,1712171,1714171,1730371,1734371,1737371,
1748471,1755571,1761671,1764671,1777771,1793971,1802081,1805081,1820281,1823281,
1824281,1826281,1829281,1831381,1832381,1842481,1851581,1853581,1856581,1865681,
1876781,1878781,1879781,1880881,1881881,1883881,1884881,1895981,1903091,1908091,
1909091,1917191,1924291,1930391,1936391,1941491,1951591,1952591,1957591,1958591,
1963691,1968691,1969691,1970791,1976791,1981891,1982891,1984891,1987891,1988891,
1993991,1995991,1998991,3001003,3002003,3007003,3016103,3026203,3064603,3065603,
3072703,3073703,3075703,3083803,3089803,3091903,3095903,3103013,3106013,3127213,
3135313,3140413,3155513,3158513,3160613,3166613,3181813,3187813,3193913,3196913,
3198913,3211123,3212123,3218123,3222223,3223223,3228223,3233323,3236323,3241423,
3245423,3252523,3256523,3258523,3260623,3267623,3272723,3283823,3285823,3286823,
3288823,3291923,3293923,3304033,3305033,3307033,3310133,3315133,3319133,3321233,
3329233,3331333,3337333,3343433,3353533,3362633,3364633,3365633,3368633,3380833,
3391933,3392933,3400043,3411143,3417143,3424243,3425243,3427243,3439343,3441443,
3443443,3444443,3447443,3449443,3452543,3460643,3466643,3470743,3479743,3485843,
3487843,3503053,3515153,3517153,3528253,3541453,3553553,3558553,3563653,3569653,
3586853,3589853,3590953,3591953,3594953,3601063,3607063,3618163,3621263,3627263,
3635363,3643463,3646463,3670763,3673763,3680863,3689863,3698963,3708073,3709073,
3716173,3717173,3721273,3722273,3728273,3732373,3743473,3746473,3762673,3763673,
3765673,3768673,3769673,3773773,3774773,3781873,3784873,3792973,3793973,3799973,
3804083,3806083,3812183,3814183,3826283,3829283,3836383,3842483,3853583,3858583,
3863683,3864683,3867683,3869683,3871783,3878783,3893983,3899983,3913193,3916193,
3918193,3924293,3927293,3931393,3938393,3942493,3946493,3948493,3964693,3970793,
3983893,3991993,3994993,3997993,3998993,7014107,7035307,7036307,7041407,7046407,
7057507,7065607,7069607,7073707,7079707,7082807,7084807,7087807,7093907,7096907,
7100017,7114117,7115117,7118117,7129217,7134317,7136317,7141417,7145417,7155517,
7156517,7158517,7159517,7177717,7190917,7194917,7215127,7226227,7246427,7249427,
7250527,7256527,7257527,7261627,7267627,7276727,7278727,7291927,7300037,7302037,
7310137,7314137,7324237,7327237,7347437,7352537,7354537,7362637,7365637,7381837,
7388837,7392937,7401047,7403047,7409047,7415147,7434347,7436347,7439347,7452547,
7461647,7466647,7472747,7475747,7485847,7486847,7489847,7493947,7507057,7508057,
7518157,7519157,7521257,7527257,7540457,7562657,7564657,7576757,7586857,7592957,
7594957,7600067,7611167,7619167,7622267,7630367,7632367,7644467,7654567,7662667,
7665667,7666667,7668667,7669667,7674767,7681867,7690967,7693967,7696967,7715177,
7718177,7722277,7729277,7733377,7742477,7747477,7750577,7758577,7764677,7772777,
7774777,7778777,7782877,7783877,7791977,7794977,7807087,7819187,7820287,7821287,
7831387,7832387,7838387,7843487,7850587,7856587,7865687,7867687,7868687,7873787,
7884887,7891987,7897987,7913197,7916197,7930397,7933397,7935397,7938397,7941497,
7943497,7949497,7957597,7958597,7960697,7977797,7984897,7985897,7987897,7996997,
9002009,9015109,9024209,9037309,9042409,9043409,9045409,9046409,9049409,9067609,
9073709,9076709,9078709,9091909,9095909,9103019,9109019,9110119,9127219,9128219,
9136319,9149419,9169619,9173719,9174719,9179719,9185819,9196919,9199919,9200029,
9209029,9212129,9217129,9222229,9223229,9230329,9231329,9255529,9269629,9271729,
9277729,9280829,9286829,9289829,9318139,9320239,9324239,9329239,9332339,9338339,
9351539,9357539,9375739,9384839,9397939,9400049,9414149,9419149,9433349,9439349,
9440449,9446449,9451549,9470749,9477749,9492949,9493949,9495949,9504059,9514159,
9526259,9529259,9547459,9556559,9558559,9561659,9577759,9583859,9585859,9586859,
9601069,9602069,9604069,9610169,9620269,9624269,9626269,9632369,9634369,9645469,
9650569,9657569,9670769,9686869,9700079,9709079,9711179,9714179,9724279,9727279,
9732379,9733379,9743479,9749479,9752579,9754579,9758579,9762679,9770779,9776779,
9779779,9781879,9782879,9787879,9788879,9795979,9801089,9807089,9809089,9817189,
9818189,9820289,9822289,9836389,9837389,9845489,9852589,9871789,9888889,9889889,
9896989,9902099,9907099,9908099,9916199,9918199,9919199,9921299,9923299,9926299,
9927299,9931399,9932399,9935399,9938399,9957599,9965699,9978799,9980899,9981899,
9989899
};
intmain()
{
int t,a,b,i,ans;
scanf("%d",&t);
while(t--)
{
years=0;
scanf("%d%d",&a,&b);
for(i=0;i<781;i++)
{
if(f[i]>=a&&f[i]<=b)
years++;
if(f[i]>b)
break;
}
printf("%d\n",ans);
}
return 0;
}