问题可以在这里找到：http ://projecteuler.net/problem=11
昨天我看到了 Euler 项目，我迷上了它。我编写了一个代码来解决问题 11，但由于某种我看不到的原因，答案是错误的。
任何人都可以阅读我的代码并提出任何建议吗？
#include <iostream>
using namespace std;
int input [20][20] = {
{8,2,22,97,38,15,0,40,0,75,4,5,7,78,52,12,50,77,91,8},
{49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48,4,56,62,0},
{81,49,31,73,55,79,14,29,93,71,40,67,53,88,30,3,49,13,36,65},
{52,70,95,23,4,60,11,42,69,24,68,56,1,32,56,71,37,2,36,91},
{22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80},
{24,47,32,60,99,3,45,2,44,75,33,53,78,36,84,20,35,17,12,50},
{32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70},
{67,26,20,68,2,62,12,20,95,63,94,39,63,8,40,91,66,49,94,21},
{24,55,58,5,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72},
{21,36,23,9,75,0,76,44,20,45,35,14,0,61,33,97,34,31,33,95},
{78,17,53,28,22,75,31,67,15,94,3,80,4,62,16,14,9,53,56,92},
{16,39,5,42,96,35,31,47,55,58,88,24,0,17,54,24,36,29,85,57},
{86,56,0,48,35,71,89,7,5,44,44,37,44,60,21,58,51,54,17,58},
{19,80,81,68,5,94,47,69,28,73,92,13,86,52,17,77,4,89,55,40},
{4,52,8,83,97,35,99,16,7,97,57,32,16,26,26,79,33,27,98,66},
{88,36,68,87,57,62,20,72,3,46,33,67,46,55,12,32,63,93,53,69},
{4,42,16,73,38,25,39,11,24,94,72,18,8,46,29,32,40,62,76,36},
{20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74,4,36,16},
{20,73,35,29,78,31,90,1,74,31,49,71,48,86,81,16,23,57,5,54},
{1,70,54,71,83,51,54,69,16,92,33,48,61,43,52,1,89,19,67,48}
};
/* if element is a[i][j], its diagonal to the right is a[i+1][j+1]
if element is a[i][j], its diagonal to the left is a[i-1][j-1]
IF element is a[i][j], the element below it is a[i+1][j]
IF element is a[i][j], the element on right of it is a[i][j+1]
*/
/*
approach:
=> find the greatest product of diagonals
=> find the greatest prodct of elements below each other
=> find the greatest prodct of element on right of each other
=> compare them
*/
int main(void)
{
unsigned long hr=0,hb=0,hdr=0, hdl=0;
//hr is the highest product on the right side traversal
//similraly for others
//for diagonal right
for(int i =0; i<17;i++) //going from 0 to 16 so that we dont land up beyond the array for (i+1),(j+1) etc
{
for(int j=0;j<17;j++)
{
if(input[i][j]*input[i+1][j+1]*input[i+2][j+2]*input[i+3][j+3] > hdr)
{
hdr = input[i][j]*input[i+1][j+1]*input[i+2][j+2]*input[i+3][j+3];
}
}
}
for(int i =19; i>=3;i--) //for diagonal left
{
for(int j=19;j>=3;j--)
{
if(input[i][j]*input[i-1][j-1]*input[i-2][j-2]*input[i-3][j-3] > hdl)
{
hdl = input[i][j]*input[i-1][j-1]*input[i-2][j-2]*input[i-3][j-3];
}
}
}
for(int i =0; i<17;i++) //for elements below each other
{
for(int j=0;j<20;j++)
{
if(input[i][j]*input[i+1][j]*input[i+2][j]*input[i+3][j] > hb)
{
hb = input[i][j]*input[i+1][j]*input[i+2][j]*input[i+3][j];
}
}
}
for(int i =0; i<20;i++) //on right
{
for(int j=0;j<17;j++)
{
if(input[i][j]*input[i][j+1]*input[i][j+2]*input[i][j+3] > hr)
{
hr = input[i][j]*input[i][j+1]*input[i][j]*input[i][j+3];
}
}
}
if(hdr>hb && hdr > hr && hdr>hdl )
{
cout<<hdr<<endl;
}
else if (hb > hdr && hb > hr && hb>hdl)
{
cout<<hb<<endl;
}
else if(hr>hb && hr> hdr && hr > hdl)
{
cout<<hr<<endl;
}
else
{
cout<<hdl<<endl;
}
return 0;
}