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#include<stdlib.h> | |
#include<stdio.h> | |
#define max(a,b) (a>b) ? a:b | |
int longest_arithmetic_progression(int a[], int n){ | |
int i,j,k; | |
int Table[n][n]; | |
int longest_ap = 2; | |
for(i=0;i<n; i++) | |
Table[i][n-1] =2; | |
for(j= n-2; j>=1; j-- ){ | |
i = j-1; | |
k = j+1; | |
while(i>=0 && k<n){ | |
if(2* a[j] > a[i] + a[k]){ | |
k++; // Table[j][k]is already filled | |
} | |
else if (2* a[j] < a[i] + a[k]){ | |
/*Table[i][j] needs to be filled before we move up */ | |
Table[i][j] =2; | |
i--; | |
} | |
else{ | |
Table[i][j] = Table[j][k] +1; | |
longest_ap = max(longest_ap, Table[i][j]); | |
i--; | |
k++; | |
} | |
} | |
while(i>=0){ | |
Table[i][j] =2; | |
i--; | |
} | |
} | |
return longest_ap; | |
} | |
int main(){ | |
int array[] = {1,7,10,13,16,19}; | |
int n = sizeof(array)/sizeof(array[0]); | |
longest_arithmetic_progression(array,n); | |
return 0; | |
} |
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