代码随想录二刷day36

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前言

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一、力扣435. 无重叠区间

class Solution {
    public int eraseOverlapIntervals(int[][] intervals) {
        Arrays.sort(intervals, (a,b) -> Integer.compare(a[0],b[0]));
        int count = 1, left = intervals[0][0], right = intervals[0][1];
        for(int i = 1; i < intervals.length; i ++){
            if(intervals[i][0] < right){
                right = Math.min(right, intervals[i][1]);
            }else{
                count ++;
                right = intervals[i][1];
            }
        }
        return intervals.length - count;
    }
}

二、力扣763. 划分字母区间

class Solution {
    public List<Integer> partitionLabels(String s) {
        List<Integer> list = new ArrayList<>();
        char[] ch = s.toCharArray();
        int[] edge = new int[27];
        for(int i = 0; i < ch.length; i ++){
            edge[ch[i] - 'a'] = i;
        }
        int last = -1, idx = 0;
        for(int i = 0; i < ch.length; i ++){
            idx = Math.max(idx, edge[ch[i] - 'a']);
            if(i == idx){
                list.add(i - last);
                last = i;
            }
        }
        return list;
    }
}

三、力扣56. 合并区间

class Solution {
    public int[][] merge(int[][] intervals) {
        List<int[]> res = new ArrayList<>();
        Arrays.sort(intervals ,(a,b)->Integer.compare(a[0],b[0]));
        int left = intervals[0][0], right = intervals[0][1];
        for(int i = 1; i < intervals.length; i ++){
            if(intervals[i][0] > right){
                res.add(new int[]{left, right});
                left = intervals[i][0];
                right = intervals[i][1];
            }else{
                right = Math.max(right, intervals[i][1]);
            }
        }
        res.add(new int[]{left, right});
        return res.toArray(new int[res.size()][]);
    }
}