|
| 1 | +packagehard; |
| 2 | + |
| 3 | +importjava.util.ArrayList; |
| 4 | +importjava.util.Arrays; |
| 5 | +importjava.util.List; |
| 6 | +importjava.util.TreeMap; |
| 7 | + |
| 8 | +publicclassTheSkylineProblem { |
| 9 | + |
| 10 | +classBuildingPointimplementsComparable<BuildingPoint>{ |
| 11 | +intx; |
| 12 | +booleanisStart; |
| 13 | +inth; |
| 14 | + |
| 15 | +publicBuildingPoint(intx,booleanisStart,inth){ |
| 16 | +this.x =x; |
| 17 | +this.h =h; |
| 18 | +this.isStart =isStart; |
| 19 | + } |
| 20 | + |
| 21 | +@Override |
| 22 | +publicintcompareTo(BuildingPointo){ |
| 23 | +if(this.x !=o.x){ |
| 24 | +returnthis.x -o.x; |
| 25 | + }else { |
| 26 | +if(this.isStart &&o.isStart){ |
| 27 | +returno.h -this.h; |
| 28 | + }elseif(this.isStart && !o.isStart){ |
| 29 | +return -this.h -o.h; |
| 30 | + }elseif(!this.isStart && !o.isStart){ |
| 31 | +returnthis.h -o.h; |
| 32 | + }else { |
| 33 | +returnthis.h +o.h; |
| 34 | + } |
| 35 | + } |
| 36 | + } |
| 37 | + } |
| 38 | + |
| 39 | +publicList<int[]>getSkyline(int[][]buildings) { |
| 40 | +BuildingPoint[]bps =newBuildingPoint[buildings.length*2]; |
| 41 | +intindex =0; |
| 42 | +for(int[]building :buildings){ |
| 43 | +BuildingPointbp1 =newBuildingPoint(building[0],true,building[2]); |
| 44 | +BuildingPointbp2 =newBuildingPoint(building[1],false,building[2]); |
| 45 | +bps[index++] =bp1; |
| 46 | +bps[index++] =bp2; |
| 47 | + } |
| 48 | + |
| 49 | +//this is one key step: |
| 50 | +Arrays.sort(bps); |
| 51 | + |
| 52 | +List<int[]>result =newArrayList(); |
| 53 | +TreeMap<Integer,Integer>treeMap =newTreeMap(); |
| 54 | +treeMap.put(0,1); |
| 55 | +intprevMaxH =0; |
| 56 | +for(BuildingPointbp :bps){ |
| 57 | +//if it's a starting point, we'll add it into the final result |
| 58 | +if(bp.isStart){ |
| 59 | +if(treeMap.containsKey(bp.h))treeMap.put(bp.h,treeMap.get(bp.h)+1); |
| 60 | +elsetreeMap.put(bp.h,1); |
| 61 | + } |
| 62 | + |
| 63 | +//if it's an ending point, we'll decrement/remove this entry |
| 64 | +elseif(!bp.isStart){ |
| 65 | +if(treeMap.containsKey(bp.h) &&treeMap.get(bp.h) >1)treeMap.put(bp.h,treeMap.get(bp.h)-1); |
| 66 | +elsetreeMap.remove(bp.h); |
| 67 | + } |
| 68 | + |
| 69 | +intcurrMaxH =treeMap.lastKey(); |
| 70 | +if(currMaxH !=prevMaxH){ |
| 71 | +result.add(newint[]{bp.x,currMaxH}); |
| 72 | +prevMaxH =currMaxH; |
| 73 | + } |
| 74 | + |
| 75 | + } |
| 76 | + |
| 77 | +returnresult; |
| 78 | + } |
| 79 | + |
| 80 | +} |