Day36 贪心算法 part05 435. 无重叠区间 763. 划分字母区间 56. 合并区间

贪心算法 part05 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 {
private:
    bool static Compare(const vector<int>& a, const vector<int>& b){
        return a[0] <b[0];
    }
public:
    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
        sort(intervals.begin(),intervals.end());
        int result = 0;
        for(int i = 0; i<intervals.size()-1;i++){
            if(intervals[i][1]>intervals[i+1][0]) 
            {
                result++;
                intervals[i+1][1] = min(intervals[i][1],intervals[i+1][1]);
            }
        }
        return result;
    }
};

763. 划分字母区间

class Solution {
public:
    vector<int> partitionLabels(string S) {
        int hash[26] = {0}; // i为字符，hash[i]为字符出现的最后位置
        for (int i = 0; i < S.size(); i++) { // 统计每一个字符最后出现的位置
            hash[S[i] - 'a'] = i;
        }
        vector<int> result;
        int left = 0;
        int right = 0;
        for (int i = 0; i < S.size(); i++) {
            right = max(right, hash[S[i] - 'a']); // 找到字符出现的最远边界
            if (i == right) {
                result.push_back(right - left + 1);
                left = i + 1;
            }
        }
        return result;
    }
};

56. 合并区间

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