@@ -28,20 +28,20 @@ public static void main(String[] args) {
2828 // lines[i][0]: 第i条线的终点
2929 // 时间复杂度O(n*(max - min))
3030 public static int maxCover (int [][] lines ) {
31- if (null == lines || lines .length < 1 ) {
31+ if (null == lines || lines .length < 1 ) {
3232 return 0 ;
3333 }
3434 int min = lines [0 ][0 ];
3535 int max = lines [0 ][1 ];
3636 for (int i = 1 ; i < lines .length ; i ++) {
37- min = Math .min (lines [i ][0 ],min );
38- max = Math .max (lines [i ][1 ],max );
37+ min = Math .min (lines [i ][0 ],min );
38+ max = Math .max (lines [i ][1 ],max );
3939 }
4040 int maxCover = 0 ;
41- for (int i = min ; i <= max ; i ++) {
41+ for (int i = min ; i <= max ; i ++) {
4242 int cover = 0 ;
4343 for (int [] line : lines ) {
44- if (line [0 ] <= i && i <= line [1 ]){
44+ if (line [0 ] <= i && i <= line [1 ]){
4545 cover ++;
4646 }
4747 }
@@ -52,27 +52,29 @@ public static int maxCover(int[][] lines) {
5252
5353 // 堆解法
5454 // O(N*logN)
55- public static int maxCover3 (int [][] lines ) {
56- if (null == lines || lines .length == 0 ) {
55+ public static int maxCover2 (int [][] lines ) {
56+ if (lines == null || lines .length < 1 ) {
5757 return 0 ;
5858 }
59- // 开始位置排序
60- Arrays .sort (lines , Comparator . comparingInt ( line -> line [0 ]) );
61- PriorityQueue <int []> heap = new PriorityQueue <>(Comparator . comparingInt ( line -> line [1 ]) );
59+ // 按开始位置排序
60+ Arrays .sort (lines , 0 , lines . length , ( a , b ) -> a [0 ] - b [ 0 ] );
61+ PriorityQueue <int []> heap = new PriorityQueue <>(( a , b ) -> a [1 ] - b [ 1 ] );
6262 int max = 0 ;
6363 for (int [] line : lines ) {
64- while (!heap .isEmpty () && heap .peek ()[1 ] < line [0 ]) {
64+ // 开始位置从小到大
65+ while (!heap .isEmpty () && line [0 ] > heap .peek ()[1 ]) {
6566 heap .poll ();
6667 }
6768 heap .offer (line );
68- max = Math .max (heap .size (), max );
69+ max = Math .max (max , heap .size ());
6970 }
7071 return max ;
7172 }
7273
74+ 7375 // 线段树解法
7476 // 复杂度是:O(N*logN)
75- public static int maxCover2 (int [][] lines ) {
77+ public static int maxCover3 (int [][] lines ) {
7678 HashMap <Integer , Integer > map = index (lines );
7779 int N = map .size ();
7880 SegmentTree tree = new SegmentTree (N );
@@ -102,7 +104,6 @@ public static HashMap<Integer, Integer> index(int[][] lines) {
102104 return map ;
103105 }
104106
105- 106107 // [1...3],[2..6],[4..9],问:哪个区间描的最多,可以用线段树(注意离散化,注意在范围内+1以后,执行的不是querySum而是queryMax)
107108 // 注意:不管什么线段,开始位置排序,线段开始位置越早,越先处理
108109 public static class SegmentTree {
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