803. 区间合并

Posted 2021-05-20 幽殇默

https://www.acwing.com/problem/content/805/
结构体写法：

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int N=1e5+10;
struct node
{
	int x,y;
}Node[N];
int n;
bool cmp(node a,node b)
{
	return a.x<b.x;
}
int main(void)
{
	cin>>n;
	int ans=1;
	for(int i=0;i<n;i++) cin>>Node[i].x>>Node[i].y;
	sort(Node,Node+n,cmp);
	int startx=Node[0].x,starty=Node[0].y;
	for(int i=1;i<n;i++) 
	{
		int x=Node[i].x,y=Node[i].y;
		if(x<=starty&&y>starty) starty=y;  
		if(x>starty) ans++,startx=x,starty=y;
	}
	cout<<ans<<endl;
}

pair写法：

#include<cstdio>
#include<iostream>
#include<map>
#include<vector>
#include<algorithm>
#define x first
#define y second
using namespace std;
typedef pair<int,int> PII;
int n;
vector<PII> ve;
int main(void)
{
    cin>>n;
    int l,r;
    for(int i=0;i<n;i++) cin>>l>>r,ve.push_back({l,r});
    sort(ve.begin(),ve.end());
    int ans=1;
    int start=ve[0].x;
    int end=ve[0].y;
    for(int i=1;i<ve.size();i++)
    {
        if(ve[i].x<=end&&ve[i].y>=end) end=ve[i].y;
        if(ve[i].x>end) ans++,start=ve[i].x,end=ve[i].y;
    }
    cout<<ans<<endl;
    return 0;
}

y总写法:

#include<cstdio>
#include<iostream>
#include<map>
#include<algorithm>
#include<vector>
#define x first
#define y second
using namespace std;
typedef pair<int,int> PII;
vector<PII> ve;
vector<PII> merge()
{
    vector<PII> res;
    int start=-2e9,end=-2e9;
    for(int i=0;i<ve.size();i++)
    {
        if(ve[i].x>end) 
        {
            if(end!=-2e9) res.push_back({start,end});
            start=ve[i].x,end=ve[i].y;
        }
        else end=max(end,ve[i].y);
    }
    if(end!=-2e9&&start!=-2e9) res.push_back({start,end});
    return res;
}
int main(void)
{
    int n; cin>>n;
    for(int i=0;i<n;i++)
    {
        int l,r;  cin>>l>>r;
        ve.push_back({l,r});
    }
    sort(ve.begin(),ve.end());
    ve=merge();
    cout<<ve.size()<<endl;
}