47 lines
893 B
C++
47 lines
893 B
C++
#include<iostream>
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#include<algorithm>
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#include<cstdio>
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using namespace std;
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const int N=100010;
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struct darling
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{
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int s,t,m,mt;
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} a[N];
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int n;
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bool cmp(darling x,darling y)
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{
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if(x.m==y.m)
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return x.s<y.s;
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return x.m<y.m;
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}
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int main()
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{
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while(~scanf("%d",&n))
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{
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if(!n)
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break;
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for(int i=0; i<n; i++)
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{
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scanf("%d%d",&a[i].s,&a[i].t);
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a[i].mt=(a[i].t-a[i].s)/2+1;
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a[i].m=a[i].s+a[i].mt;
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}
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sort(a,a+n,cmp);
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int i=0;
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for(int t=0; i<n; i++)
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{
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if(t>a[i].t-a[i].mt)
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break;
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if(t>=a[i].s)
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t+=a[i].mt;
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else
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t=a[i].m;
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}
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if(i==n)
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printf("YES\n");
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else
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printf("NO\n");
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}
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return 0;
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}
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