### How Can I Directly Use The Iterator Values?

Hello Professionals:

Good day. I am honestly a newbie of std::vector and I would like to know how can I convert my previous program into a new one? My old program looks like this:

 ``1234567891011121314`` ``````float matA2[1000][1000]; int a = 0; for (int x = 0; x < count_g_polCoeffGerald; x++) { int b = 0; for (int y = 0; y < count_g_polCoeffGerald; y++) { x0 = values [a]; //x component y0 = values [a + 1]; //y component x1 = values [b] //x component of the next coordinate y1 = values [b + 1]; //y component of the next coordinate matA2[x][y] = LeastSquareDistance(x0,y0,x1,y1); //function computation b+=2; //go to next coordinate } a+=2; //go to next coordinate to be compared with all coordinates }``````

However, I am trying to incorporate the same algorithm to the code that I have right now, but I am having trouble with how can I can call the x,y,z values of indCell. I know that the code "glm::ivec3 indCell = it->first;" iterates to all the values of g_polCoeff and "indCell.x", "indCell.y" correspond to "x values" and "y values" of indCell, however, I was wondering how can I call the next x,y values of the next coordinate if I have the kind of syntax code below considering the iterator "it" I have below?

 ``123456789101112131415161718192021222324`` ``````std::unordered_map::iterator it; const int count_g_polCoeff = g_polCoeff.size(); for (it = g_polCoeff.begin(); it != g_polCoeff.end(); it++) { glm::ivec3 indCell = it->first; std::vector matA2; matA2.reserve(count_g_polCoeff * count_g_polCoeff); int a = 0; for (int x = 0; x < count_g_polCoeffGerald; x++) { int b = 0; for (int y = 0; y < count_g_polCoeffGerald; y++) { x0 = ? y0 = ? x1 = ? y1 = ? matA2[ ] = LeastSquareDistance(x0,y0,x1,y1); b+=2; //go to next coordinate } a+=2; //go to next coordinate to be compared with all coordinates } }``````

Up to this moment I am still guessing how to correspondingly translate my old program to the new one and it's still question mark for me. Thank you very much for your inputs in advance!
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 ``12345678`` ``````std::unordered_map::iterator a, b; a = b = g_polCoeff.begin(); ++b; x0 = a->first.x; y0 = a->first.y; x1 = b->first.x; y1 = b->first.y;``````
notice that when `a' is pointing to the last element in your collection, `b' will be invalid.

 ``12345`` ``````matA2.reserve(count_g_polCoeff * count_g_polCoeff); //... matA2.push_back(LeastSquareDistance(x0,y0,x1,y1)); //later if you want to access cell (x,y) matA2[x*number_of_columns + y]``````
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