352[LeetCode] Data Stream as Disjoint Intervals

Posted 2021-02-10 WhoDreamsSky

Given a data stream input of non-negative integers a1, a2, ..., an, ..., summarize the numbers seen so far as a list of disjoint intervals.

For example, suppose the integers from the data stream are 1, 3, 7, 2, 6, ..., then the summary will be:

[1, 1]
[1, 1], [3, 3]
[1, 1], [3, 3], [7, 7]
[1, 3], [7, 7]
[1, 3], [6, 7]

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#include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>

using namespace std;
 
                        


struct Interval {
    int start;
    int end;
    Interval() : start(0), end(0) {}
    Interval(int s, int e) : start(s), end(e) {}
};

bool Cmp(Interval a, Interval b) { return a.start < b.start; }//不能将其放在class SummaryRange中

class SummaryRanges {
public:
    void addNum(int val) {
        
        vector<Interval>::iterator it = lower_bound(vec.begin(), vec.end(), Interval(val, val), Cmp);
        int start = val, end = val;
        if(it != vec.begin() && (it-1)->end+1 >= val) it--;
        while(it != vec.end() && val+1 >= it->start && val-1 <= it->end)
        {
            start = min(start, it->start);
            end = max(end, it->end);
            it = vec.erase(it);
        }
        vec.insert(it,Interval(start, end));
    }
    
    vector<Interval> getIntervals() {
        return vec;
    }
private:
    vector<Interval> vec;
};

/**
 * Your SummaryRanges object will be instantiated and called as such:
 * SummaryRanges* obj = new SummaryRanges();
 * obj->addNum(val);
 * vector<Interval> param_2 = obj->getIntervals();
 */
 
 
 int main(){
     SummaryRanges* obj =new SummaryRanges();
     obj->addNum(1);
     obj->addNum(2);
    obj->addNum(5);
     obj->addNum(6);
     obj->addNum(3);
     vector<Interval> param_2 = obj->getIntervals();
     cout<<param_2[0].start<<"------"<<param_2[0].end<<endl;
     cout<<param_2[1].start<<"------"<<param_2[1].end<<endl;
 }

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易错点：

vector<Interval>::iterator it = lower_bound(vec.begin(), vec.end(), Interval(val, val), Cmp);
lower_bound()返回的是从begin到end之间的按照Cmp排序的首个大于等于Interval(val,val)的地址；
因此it 声明应该是  vector<Interval>::iterator it
之前错误的声明为  Interval* it  则出现报错：[Error] cannot convert ‘__gnu_cxx::__normal_iterator<Interval*, std::vector<Interval> >‘ to ‘Interval*‘ in initialization

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