# TADM2E 4.8

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Revision as of 18:23, 11 September 2014 by Algowikiadmin (Talk | contribs)

(a):

Sort S with any nlogn sorting method of your choice. for( int i = 1; i <= n; ++i ) { int j = x - S[i]; Binary search for j in the sub-array of S[i+1~n] and close the problem once it's been found; }

(b):

Subtract each of S[1~n] from x to get a new array of real numbers T[1~n]. int i = 1, j = 1; while( i <=n && j <= n ) { if( S[i] == T[j] ) { problem solved; break; } else { S[i] < T[j] ? ++i : ++j; } }

Another Solution to part B without creating the additional Array..

i = 0; j = n - 1; for (i = 0; i < j; i++) { while( (i < j) && (S[j] + S[i] > x ) { j--; } if (x == (S[j] + S[i]) { return (S[i],S[j]); break; } } "i" scans from left to right, "j" from right to left, looking for the right pair...