closestPair[ptsIn_] :=
 Module[{xP, yP,
   pts},(*Top level function.Sorts the pts by x and by y and then \
calls closestPairR[]*)pts = N[ptsIn];
  xP = Sort[pts, #1[[1]] < #2[[1]] &];
  yP = Sort[pts, #1[[2]] < #2[[2]] &];
  closestPairR[xP, yP]]

closestPairR[xP_, yP_] :=
 Module[{n, mid, xL, xR, xm, yL, yR, dL, pairL, dmin, pairMin, yS, nS,
    closest, closestP, k,
   cDist},(*where xP is P(1).. P(n) sorted by x coordinate,
  and yP is P(1).. P(n) sorted by y coordinate (ascending order)*)
  n = Length[xP];
  If[n <= 3,(*Brute Force*)
   Piecewise[{{{\[Infinity], {}},
      n < 2}, {{EuclideanDistance[xP[[1]], xP[[2]]], {xP[[1]],
        xP[[2]]}},
      n == 2}, {Last@
       MinimalBy[{{EuclideanDistance[xP[[1]], xP[[2]]], {xP[[1]],
           xP[[2]]}}, {EuclideanDistance[xP[[1]], xP[[3]]], {xP[[1]],
           xP[[3]]}}, {EuclideanDistance[xP[[3]], xP[[2]]], {xP[[3]],
           xP[[2]]}}}, First], n == 3}}], mid = Ceiling[n/2];
   xL = xP[[1 ;; mid]];
   xR = xP[[mid + 1 ;; n]];
   xm = xP[[mid]];
   yL = Select[yP, #[[1]] <= xm[[1]] &];
   yR = Select[yP, #[[1]] > xm[[1]] &];
   {dL, pairL} = closestPairR[xL, yL];
   {dmin, pairMin} = closestPairR[xR, yR];
   If[dL < dmin, {dmin, pairMin} = {dL, pairL}];
   yS = Select[yP, Abs[#[[1]] - xm[[1]]] <= dmin &];
   nS = Length[yS];
   {closest, closestP} = {dmin, pairMin};
   Table[k = i + 1;
    While[(k <= nS) && (yS[[k, 2]] - yS[[i, 2]] < dmin),
     cDist = EuclideanDistance[yS[[k]], yS[[i]]];
     If[cDist <
       closest, {closest, closestP} = {cDist, {yS[[k]], yS[[i]]}}];
     k = k + 1], {i, 1, nS - 1}];
   {closest, closestP}](*end if*)]