差分数组——面对大数据的处理

#include <iostream>
#include <map>
using namespace std;
long long int cun[200010];
map<long long int, long long int>num;
map<long long int, long long int>::iterator it;
int main()
{
    long long int n;
    long long int l, r;
    cin >> n;
    
    for (int i = 1; i <= n; i++)
    {
        
        cin >> l >> r;
        num[l]++;
        num[r + 1]--;
    }//以上和差分数组完全一致
    long long int cnt = 0;
    it=num.begin();
    long long int cmp = it->first;

    for ( it = num.begin(); it != num.end(); it++)//巧妙之处
    {//cnt的计算和差分数组计算次数的方法一样
        cun[cnt] += it->first-cmp;//能算出这个点距离上次出现的端点多远了
        cmp = it->first;
        cnt += it->second;
    }
    for (int i = 1; i <= n; i++)
    {
        if (i != 1)cout << " ";
        cout << cun[i];
    }
    return 0;
}