Lecture20

# Lecture20 - ECS 30 Introduction to Programming and Problem...

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ECS 30 Introduction to Programming and Problem Solving François Gygi Department of Computer Science

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Lecture 20 • Chapter 8 • Complexity of algorithms: sorting • Using multidimensional arrays
bubble sort implementation int ordered = 0; while (!ordered) { int restart = 0; for ( i=0; i<n-1 && !restart; i++ ) { if ( x[i] > x[i+1] ) { swap(&x[i],&x[i+1]); restart = 1; } else if ( i == n-2 ) ordered = 1; } } program bubble.c

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int x[5] = { 11, 7, 3, 4, 9 }; swap(&x[0],&x[2]); /* { 3, 7, 11, 4, 9 } */ swap(&x[1],&x[3]); /* { 3, 4, 11, 7, 9 } */ swap(&x[2],&x[3]); /* { 3, 4, 7, 11, 9 } */ swap(&x[3],&x[4]); /* { 3, 4, 7, 9, 11 } */ /* done */ Selection sort: search for smallest element and swap
selection sort implementation int get_min(int[] a, int first, int last); { int i, i_small=first, small=a[first]; for ( i=first; i<=last; i++ ) if ( a[i] < small ) { small = a[i]; i_small = i; } return i_small; }

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selection sort implementation int i, i_min; for ( i=0; i<n-1; i++ ) { /* find position of the smallest element in [i,n-1] */ i_min = get_min(x,i,n-1); if ( i_min != i ) swap(&x[i],&x[i_min]); }
Searching: Finding an element in an array int x[5]; int target_val = 3; int i = 0, found = 0; while ( i < n && !found ) { found = (x[i++] == target_val); } program search.c

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## This note was uploaded on 01/21/2012 for the course ECON 2a taught by Professor Xi during the Spring '11 term at Cornell College.

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Lecture20 - ECS 30 Introduction to Programming and Problem...

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