Southern Subregion Problem K. Road Work

贪心

#include <bits/stdc++.h>
using namespace std;
const int maxn=300050;
int d[maxn]; 
vector<int>L;
vector<int>R;
int main(){
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		scanf("%d",&d[i]);
	}
	for(int i=1;i<=n;i++){
		int r=0x3f3f3f3f;
		int wh,ans1,ans2;
		for(int j=i;j<=n;j++){
			r=min(min(n,r),j+d[j]-1);
			if(j==r){
				ans1=j;
				break;
			}
		}
		for(int j=i;j<=n;j++){
			int l_now=max(i,j-d[j]+1);
			if(l_now>i) break;
			else ans2=j;
		}
		wh=max(ans1,ans2);
		if(ans1<ans2){
			L.push_back(i);
			R.push_back(wh);
		}
		else {
			L.push_back(wh);
			R.push_back(i);
		}
		i=wh;
	}
	int siz=L.size();
	cout<<siz<<endl;
	for(int i=0;i<siz;i++){
		cout<<L[i]<<" "<<R[i]<<endl;
	}
}