[英]traverse in vector<vector<pair<int, int> > >
I came across a situation that I couldn't explain why.我遇到了一个我无法解释原因的情况。 I have a
vector<vector<pair<int, int> > > parent
that indicates parent
of a specific cell.我有一个
vector<vector<pair<int, int> > > parent
表示特定单元格的parent
。 I have following code:我有以下代码:
// (1, 0), (1, 2), (1, 2)
// (1, 2), (-1, -1), (1, 2)
// (-1, -1), (2, 1), (-1, -1)
vector<vector<pair<int, int> > > nums = {
{make_pair(1, 0), make_pair(1, 2), make_pair(1, 2)},
{make_pair(1, 2), make_pair(-1, -1), make_pair(1, 2)},
{make_pair(-1, -1), make_pair(2, 1), make_pair(-1, -1)}};
int r = 0;
int c = 1;
while (nums[r][c] != make_pair(r, c)) {
cout << nums[r][c].first << " " << nums[r][c].second << endl; // 1, 2
r = nums[r][c].first; // 1
c = nums[r][c].second; // -1
cout << "r: " << r << " c: " << c << endl;
}
I 'm not sure why in the first iteration of while
loop for c = nums[r][c].second;
我不知道为什么在
while
循环的第一次迭代中c = nums[r][c].second;
it returns -1 instead of 2.它返回 -1 而不是 2。
In first iteration,在第一次迭代中,
r=num[0][1].first = 1.
Therefore所以
c=num[1][1].second = - 1.
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