代码随想录算法训练营第三十六天|435. 无重叠区间 ● 763.划分字母区间 ● 56. 合并区间

435. 无重叠区间 

class Solution {
public:
static bool cmp(const vector<int>& a,const vector<int>& b){
    return a[0]<b[0];
}
    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
        int k=0;
        sort(intervals.begin(),intervals.end(),cmp);
        for(int i=1;i<intervals.size();i++){
            if(intervals[i-1][1]>intervals[i][0]){
                k++;
                intervals[i][1]=min(intervals[i-1][1],intervals[i][1]);
            }
        }
        
        return k;
    }
};

763.划分字母区间 

class Solution {
public:
    vector<int> partitionLabels(string s) {
        vector<int> ret;
        vector<int> a(27, 0);
        for (int i = 0; i < s.size(); i++)
            a[s[i] - 'a'] = i;
        int f = -1;
        int k = 0;
        for (int i = 0; i < s.size(); i++) {
            if (a[s[i] - 'a'] > f)
                f = a[s[i] - 'a'];
            if (f == i) {
                ret.push_back(i - k + 1);
                k = f+1;//左边界要往前移动一格
            }
        }
        return ret;
    }
};

56. 合并区间 

class Solution {
public:
    static bool cmp(const vector<int>& a, const vector<int>& b) {
        return a[0] < b[0];
    }
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
       vector<vector<int>> a;
        sort(intervals.begin(), intervals.end(), cmp);
        a.push_back(intervals[0]);
        for(int i=1;i<intervals.size();i++){
            if(a.back()[1]>=intervals[i][0]){
                a.back()[1]=max(a.back()[1],intervals[i][1]);
            }
            else{
                a.push_back(intervals[i]);
            }
        }
        return a;
    }
};