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const title = "최소 신장 트리 · 간선 선택";
const canvas = document.getElementById('stage');
const ctx = canvas.getContext('2d');
const restart = document.getElementById('restart');
const step = document.getElementById('step');
const speed = document.getElementById('speed');
let index = 0, last = performance.now(), width = 300, height = 200;
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function text(value,x,y,color,size=12,align='left'){ ctx.fillStyle=color;ctx.font='600 '+size+'px sans-serif';ctx.textAlign=align;ctx.textBaseline='middle';ctx.fillText(String(value),x,y); }
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function dot(x,y,r,color){ctx.fillStyle=color;ctx.beginPath();ctx.arc(x,y,r,0,Math.PI*2);ctx.fill();}
function draw(){
if(!frames.length)return;
const p=colors(), frame=frames[index], d=frame.data, detail=width>500;
ctx.fillStyle=p.bg;ctx.fillRect(0,0,width,height);
text(title,12,18,p.fg,detail?16:13);text(frame.caption,12,detail?43:39,p.muted,detail?13:10);
text((index+1)+' / '+frames.length,width-12,18,p.muted,10,'right');
const top=detail?62:53, bottom=detail?height-47:height-9, span=Math.max(10,bottom-top), areaW=Math.min(width-22,detail?710:width-22), left=(width-areaW)/2;
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const chosen=d.selected?.includes(key), active=d.activeEdge===key;ctx.globalAlpha=active||chosen?1:.58;line(pa.x,pa.y,pb.x,pb.y,active?p.accent2:chosen?p.accent:p.muted,active?4:chosen?3:2);ctx.globalAlpha=1;
if(d.directed){const angle=Math.atan2(pb.y-pa.y,pb.x-pa.x),x=pb.x-Math.cos(angle)*(detail?18:13),y=pb.y-Math.sin(angle)*(detail?18:13);line(x-Math.cos(angle-.55)*7,y-Math.sin(angle-.55)*7,x,y,p.muted,1.5);line(x-Math.cos(angle+.55)*7,y-Math.sin(angle+.55)*7,x,y,p.muted,1.5);}
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if(d.groups){const group=d.groups[nodes.findIndex(n=>n.id===node.id)];color=[p.accent,p.accent2,p.accent3][nodes.findIndex(n=>n.id===group)%3];}
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if(d.distances)text(Number.isFinite(d.distances[node.id])?d.distances[node.id]:'∞',pt.x,pt.y+(detail?29:22),p.muted,10,'center');
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const table=frame.kind==='table',bits=frame.kind==='bits';const rows=bits?1:table?d.values.length:d.rows,cols=bits?d.bits.length:table?d.values[0].length:d.cols;
const labelX=table?24:0,labelY=table?18:0,cell=Math.min((areaW-labelX)/cols,(span-labelY)/rows,detail?56:32),ox=left+(areaW-(cols*cell+labelX))/2+labelX,oy=top+(span-(rows*cell+labelY))/2+labelY;
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ctx.fillStyle=blocked?p.line:active?p.accent2:path||queen?p.accent3:front?p.accent2:visited?p.accent:source?p.accent3:bits&&d.bits[c]?p.accent:p.surface;ctx.fillRect(x+2,y+2,cell-4,cell-4);ctx.strokeStyle=p.muted;ctx.globalAlpha=.42;ctx.strokeRect(x+1,y+1,cell-2,cell-2);ctx.globalAlpha=1;
const value=bits?d.bits[c]:table?d.values[r][c]:queen?'Q':d.start===n?'S':d.goal===n?'G':blocked?'':visited?'·':'';
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if(bits)text(c,x+cell/2,y+cell+11,p.muted,9,'center');
}
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const rowH=Math.min(31,span/d.intervals.length),unit=(areaW-28)/10,ox=left+10,oy=top+(span-rowH*d.intervals.length)/2;
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const cx=width/2,cy=top+span/2,r=Math.min(areaW,span)*.35,loc=(v,rr)=>({x:cx+Math.sin(v*2*Math.PI)*rr,y:cy-Math.cos(v*2*Math.PI)*rr});ctx.strokeStyle=p.muted;ctx.globalAlpha=.6;ctx.lineWidth=2;ctx.beginPath();ctx.arc(cx,cy,r,0,Math.PI*2);ctx.stroke();ctx.globalAlpha=1;
d.keys.forEach((key,i)=>{const point=loc(key,r),server=d.servers.find(s=>s.id===d.owners[i]),dest=loc(server.pos,r);line(point.x,point.y,dest.x,dest.y,d.active===i?p.accent2:p.line,1);dot(point.x,point.y,d.active===i?6:4,d.active===i?p.accent2:p.fg);});
d.servers.forEach((server,i)=>{const point=loc(server.pos,r);dot(point.x,point.y,detail?15:11,[p.accent,p.accent2,p.accent3,p.fg][i]);text(server.id,point.x,point.y,i===3?p.bg:'#fff',11,'center');});
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const side=Math.min(areaW,span)-8,ox=(width-side)/2,oy=top+(span-side)/2;ctx.strokeStyle=p.muted;ctx.globalAlpha=.5;ctx.strokeRect(ox,oy,side,side);ctx.globalAlpha=1;ctx.beginPath();ctx.arc(ox,oy+side,side,Math.PI*1.5,0);ctx.strokeStyle=p.muted;ctx.stroke();
d.points.forEach(([x,y])=>dot(ox+x*side,oy+side-y*side,detail?2.5:1.7,x*x+y*y<=1?p.accent:p.accent2));
}
}
function advance(){index=(index+1)%frames.length;draw();}
restart.addEventListener('click',()=>{index=0;last=performance.now();draw();});
step.addEventListener('click',()=>{advance();last=performance.now();});
addEventListener('resize',resize);resize();
function loop(now){const delay=900-Number(speed.value)*140;if(now-last>delay){advance();last=now;}requestAnimationFrame(loop);}requestAnimationFrame(loop);
