对于任何论坛礼仪错误，我提前道歉，这是我的第一篇文章。
无论如何，我一直在为 projecteuler.com 问题编写代码，现在无论我如何尝试修复它，程序第二次返回 0。我正在用 C 编码。
**欧拉项目剧透警报** * ** * *
第一个遇到这个问题的程序是找到最大的回文数，该回文数可以通过将两个三位数相乘得到。
/* this is a program to find the largest palindrome produced
by two factors of n digits each */
// test combos of n digit factors for palindrome product
// run backwards to optimize speed for finding largest
// design should work for user input number of digits to be multiplied
#include <stdio.h>
int main()
{
// declare and value vars
int n; // number of digits
int nsub; // for first while loop
int a = 0; // count down 1
int b = 0; // count down 2
int c; // counter
int d; // digit to be moved in palindrome checker algorithm
int e; // translates to true/false for palindrome
int t1; // number to be tested for... (palindromnity? palindromicness?)
int t3 = 0; // just another variable in my palindrome checker
int t4; // aaand another variable
int p; // current leading largest palindrome
// get user input for number of digits
printf("Please input the number of digits (<5 recommended) you \n");
printf("would like in the two factors that will be multiplied \n");
printf("to find the largest palindrome they can produce\n");
scanf("%d", &n);
// translate number of digits to count down start
nsub = n;
while ( nsub > 0 )
{
a = 10 * a + 9;
b = a;
nsub--;
}
int i = a; // random int to avoid 'change in a' problem
// start of finding stuff algorithm
for ( c=0 ; c < i ; c++ )
{
// loop to run through all b vals on one a val
while( b > 0 )
{
t1 = a * b;
// this will allow a check for an any digit palindrome
/* the program will remove the last digit (d) from the
(number that is hopefully a palindrome) and move
it as the first digit in a new number to be compared
to the original. before comparing the numbers with
d moved to the other, it will compare them with d
having been completely removed. this way even and odd
digit palindromes will register correct. */
t4 = t1;
while( t4 > 0 )
{
e = 1;
d = t4 % 10;
t4 = (t4 - d)/10;
if( t4 == t3 )
{
e = 0;
break;
}
t3 = 10 * t3 + d;
if( t4 == t3 )
{
e = 0;
break;
}
}
// e = 0 means it is a palindrome
if(e == 0 && p < t1)
{
p = t1;
// p is the current leading largest palindrome
}
b--;
}
// resets at next a val with equal b val
a--;
b = a;
}
printf("The largest palindrome that is the product\n");
printf("of two numbers of %d digits is: %d\n", n, p);
getchar(); // extra for input
getchar();
return 0;
}
无论我使用多少位数，程序总是说我的答案是 0。
下一个遇到这个问题的程序是在一个 1000 位数字中找到五个连续数字的最大乘积。这仍在进行中。
/*
73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450
*/
/* this is a program to find the greatest
product of five consecutive digits in the
1000 digit number above.
*/
#include <stdio.h>
#include <string.h>
int main()
{
char str[1001] = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450";
int p; // current product
int g = 0; // current greatest product
int a=5; // counter
while( a != 1001 )
{
str[a]*str[a-1]*str[a-2]*str[a-3]*str[a-4] = p;
if( p > g )
{
g = p;
}
else
{
}
a++;
}
printf("%d is the largest product of five consecutive numbers", g);
getchar();
return 0;
}
谢谢，我已经看过一百万次了，不知道它会是什么。