Insert Interval leetcode java

題目：

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

Example 1:
Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9].

Example 2:
Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16].

This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10].

 

題解：

這道題不僅要insert newInterval同時還要保證能夠merge。那么就分情況討論。

遍歷每一個已給出的interval，

當當前的interval的end小於newInterval的start時，說明新的區間在當前遍歷到的區間的后面，並且沒有重疊，所以res添加當前的interval；

當當前的interval的start大於newInterval的end時，說明新的區間比當前遍歷到的區間要前面，並且也沒有重疊，所以把newInterval添加到res里，並更新newInterval為當前的interval；

當當前的interval與newInterval有重疊時，merge interval並更新新的newInterval為merge后的。

 

代碼如下：

 

 
           1      
          public ArrayList<Interval> insert(ArrayList<Interval> intervals, Interval newInterval) { 
          
 
           2         ArrayList<Interval> res =  
          new ArrayList<Interval>(); 
          
 
           3              
          
 
           4          
          for(Interval each: intervals){ 
          
 
           5              
          if(each.end < newInterval.start){ 
          
 
           6                 res.add(each); 
          
 
           7             } 
          else  
          if(each.start > newInterval.end){ 
          
 
           8                 res.add(newInterval); 
          
 
           9                 newInterval = each;         
          
 
          10             } 
          else  
          if(each.end >= newInterval.start || each.start <= newInterval.end){ 
          
 
          11                  
          int nstart = Math.min(each.start, newInterval.start); 
          
 
          12                  
          int nend = Math.max(newInterval.end, each.end); 
          
 
          13                 newInterval =  
          new Interval(nstart, nend); 
          
 
          14             } 
          
 
          15         } 
          
 
          16   
          
 
          17         res.add(newInterval);  
          
 
          18   
          
 
          19          
          return res; 
          
 
          20     } 
         

 Reference：//http://www.programcreek.com/2012/12/leetcode-insert-interval/