/* SudokuPuzz.com – sudoku solver */
(function(){
var root=document.querySelector(".solver");if(!root)return;
var board=root.querySelector(".sv-board"),msg=root.querySelector(".sv-msg"),inputs=[],i;
var R=[],C=[],B=[];for(i=0;i<81;i++){R[i]=(i/9)|0;C[i]=i%9;B[i]=((R[i]/3)|0)*3+((C[i]/3)|0)}
var EXAMPLE="530070000600195000098000060800060003400803001700020006060000280000419005000080079";
for(i=0;i<81;i++){(function(i){
 var el=document.createElement("input");el.type="text";el.inputMode="numeric";el.maxLength=1;el.autocomplete="off";
 el.className="sv-cell"+(C[i]%3===2&&C[i]<8?" br":"")+(R[i]%3===2&&R[i]<8?" bb":"");
 el.id="sv"+i;el.setAttribute("aria-label","Row "+(R[i]+1)+", column "+(C[i]+1));
 el.addEventListener("input",function(){el.value=el.value.replace(/[^1-9]/g,"").slice(-1);el.classList.remove("solved");mark()});
 el.addEventListener("keydown",function(e){var m={ArrowUp:-9,ArrowDown:9,ArrowLeft:-1,ArrowRight:1}[e.key];
  if(m){var n=i+m;if(n>=0&&n<81&&(Math.abs(m)===9||R[n]===R[i])){e.preventDefault();inputs[n].focus();inputs[n].select()}}});
 board.appendChild(el);inputs.push(el)})(i)}
function read(){return inputs.map(function(el){return el.classList.contains("solved")?0:(+el.value||0)})}
function conflicts(g){var bad=[];for(var i=0;i<81;i++)if(g[i])for(var j=0;j<81;j++)if(j!==i&&g[j]===g[i]&&(R[j]===R[i]||C[j]===C[i]||B[j]===B[i])){bad.push(i);break}return bad}
function mark(){var bad=conflicts(read());inputs.forEach(function(el,i){el.classList.toggle("bad",bad.indexOf(i)>=0)});return bad}
function pop(m){var n=0;while(m){m&=m-1;n++}return n}
function solve(grid,limit){
 var g=grid.slice(),rm=[0,0,0,0,0,0,0,0,0],cm=rm.slice(),bm=rm.slice(),count=0,sol=null,steps=0;
 for(var i=0;i<81;i++)if(g[i]){var b=1<<g[i];rm[R[i]]|=b;cm[C[i]]|=b;bm[B[i]]|=b}
 (function rec(){
  if(++steps>2e6)return;
  var best=-1,mask=0,bn=10;
  for(var i=0;i<81;i++)if(!g[i]){var m=~(rm[R[i]]|cm[C[i]]|bm[B[i]])&0x3FE,n=pop(m);if(n<bn){bn=n;best=i;mask=m;if(n<2)break}}
  if(best<0){count++;if(!sol)sol=g.slice();return}
  if(!bn)return;
  for(var d=1;d<=9;d++)if(mask&(1<<d)){var bit=1<<d,r=R[best],c=C[best],x=B[best];g[best]=d;rm[r]|=bit;cm[c]|=bit;bm[x]|=bit;rec();g[best]=0;rm[r]^=bit;cm[c]^=bit;bm[x]^=bit;if(count>=limit)return}
 })();
 return{count:count,solution:sol};
}
function prepare(){
 var g=read(),given=g.filter(Boolean).length;
 if(mark().length){msg.textContent="Some numbers clash with each other (shown in red). Fix them first.";return null}
 if(given<17){msg.textContent="Enter at least 17 numbers. A real sudoku never has fewer.";return null}
 var res=solve(g,2);
 if(!res.count){msg.textContent="This sudoku has no solution. Check that you typed the numbers correctly.";return null}
 return{g:g,res:res};
}
root.querySelector(".sv-solve").onclick=function(){
 var p=prepare();if(!p)return;
 p.res.solution.forEach(function(v,i){if(!p.g[i]){inputs[i].value=v;inputs[i].classList.add("solved")}});
 msg.textContent=p.res.count>1?"Solved. Note: this puzzle has more than one solution, so this is just one of them.":"Solved! The numbers in blue were filled in by the solver.";
};
root.querySelector(".sv-hint").onclick=function(){
 var p=prepare();if(!p)return;var best=-1,bn=10;
 for(var i=0;i<81;i++)if(!p.g[i]){var used=0;for(var j=0;j<81;j++)if(p.g[j]&&(R[j]===R[i]||C[j]===C[i]||B[j]===B[i]))used|=1<<p.g[j];var n=9-pop(used);if(n<bn){bn=n;best=i}}
 if(best<0){msg.textContent="The puzzle is already complete.";return}
 inputs[best].value=p.res.solution[best];inputs[best].classList.add("solved");inputs[best].focus();
 msg.textContent="Row "+(R[best]+1)+", column "+(C[best]+1)+" must be "+p.res.solution[best]+(bn===1?". It is the only number that fits there.":".");
};
root.querySelector(".sv-example").onclick=function(){inputs.forEach(function(el,i){el.value=EXAMPLE[i]==="0"?"":EXAMPLE[i];el.classList.remove("solved","bad")});msg.textContent="Example loaded. Press Solve it, or Show one number for a hint."};
root.querySelector(".sv-clear").onclick=function(){inputs.forEach(function(el){el.value="";el.classList.remove("solved","bad")});msg.textContent="Grid cleared. Type in your puzzle.";inputs[0].focus()};
})();