43 lines
812 B
C++
43 lines
812 B
C++
#include<stdio.h>
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struct Point
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{
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int x,y;
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};
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typedef struct Point point;
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int main()
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{
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point a[10001],s,t;
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int i,n,flag;
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while(scanf("%d",&n)!=EOF&&n!=0)
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{
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flag=1;
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for(i=0;i<n;i++)
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{
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scanf("%d %d",&a[i].x,&a[i].y);
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}
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a[n]=a[0];
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a[n+1]=a[1];
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for(i=0;i<n;i++)
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{
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s.x=a[i+1].x-a[i].x;
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s.y=a[i+1].y-a[i].y;
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t.x=a[i+2].x-a[i+1].x;
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t.y=a[i+2].y-a[i+1].y;
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if((s.x*t.y-s.y*t.x)<0)
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{
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flag=0;
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break;
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}
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}
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if(flag)
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{
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printf("convex\n");
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}
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else
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{
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printf("concave\n");
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}
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}
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return 0;
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}
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