[英]sort 2-d array using stl sort()
I have a 2-d array, containing only 0 or 1. I want to sort it in descend order on rows (no change on each column) using STL sort algorithm. 我有一个二维数组,仅包含0或1。我想使用STL排序算法对行进行降序排序(每列均无变化)。 but I don't know how to pass the parameter and how to write the compare function in sort(first, last, comp); 但我不知道如何传递参数以及如何在sort(first,last,comp);中编写比较函数; like: 喜欢:
0 1 1 1
1 1 0 1
1 0 1 0
would be sorted like this: 会像这样排序:
1 1 0 1
1 0 1 0
0 1 1 1
my data structure is like this: 我的数据结构是这样的:
int **table = 0;
table = new int *[row];
for(int i=0;i<row;i++)
table[i] = new int[column];
I can only write the sort function like this: 我只能这样写sort函数:
sort(a[0], a[0]+row, compare_function);
bool compare_function(int a[], int b[])
{
int i =0;
while(a[i]==0 ||a[i]==1)
{
if(a[i]>b[i])
return true;
else
i++;
}
return false;
}
But it doesn't work. 但这是行不通的。 Can some one help me? 有人能帮我吗? Thank you very much. 非常感谢你。
Change your compare function to: 将您的比较功能更改为:
bool comp(const int a[], const int b[]){
int sum1 = std::accumulate(a, a + column, 0);
int sum2 = std::accumulate(b, b + column, 0);
return sum1 < sum2;
}
Your call to sort looks wrong to me (though you never said what a
is). 您的排序请求对我来说似乎是错误的(尽管您从未说过a
是什么)。 It should be sort(table, table+row, compare_function)
它应该是sort(table, table+row, compare_function)
But I'd do it a bit differently anyway ( std::lexicographical_compare
comes from <algorithm>
): 但是无论如何我还是会做一些不同的事情( std::lexicographical_compare
来自<algorithm>
):
struct compare_rows {
const int cols;
compare_rows(int cols_) : cols(cols_) {}
bool operator()(const int a[], const int b[]) const {
// a b reversed to give descending sort
return lexicographical_compare(b, b+cols, a, a+cols);
}
};
And use it like: 并像这样使用它:
sort(table, table+row, compare_rows(column))
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