a580e1 2000-09-27 Fredrik Hübinette (Hubbe) #pike __REAL_VERSION__ a20af6 2000-09-26 Fredrik Hübinette (Hubbe) 5b9188 2006-04-24 Robert Hinn //! This class implements a (min-)heap. The value of a child node will //! always be greater than or equal to the value of its parent node. //! Thus, the top node of the heap will always hold the smallest value. b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) #define SWAP(X,Y) do{ mixed tmp=values[X]; values[X]=values[Y]; values[Y]=tmp; }while(0) static private array values=allocate(10); static private int num_values; #ifdef DEBUG void verify_heap() { int e; for(e=1;e values[e]) { b2ee5b 2001-11-22 Martin Nilsson write(sprintf("Error in HEAP (%d, %d) num_values=%d\n", (e-1)/2, e, num_values)); b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) exit(1); } } } #else #define verify_heap() #endif static void adjust_down(int elem) { int steps; while(1) { int child=elem*2+1; if(child >= num_values) break; if(child+1==num_values || values[child] < values[child+1]) { if(values[child] < values[elem]) { SWAP(child, elem); elem=child; continue; } } else { if(child+1 >= num_values) break; if(values[child+1] < values[elem]) { SWAP(elem, child+1); elem=child+1; continue; } } break; } } static int adjust_up(int elem) { int parent=(elem-1)/2; 4720a6 1999-12-30 Fredrik Hübinette (Hubbe) af0035 1999-12-31 Fredrik Hübinette (Hubbe) if(elem && values[elem] < values[parent]) b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) { SWAP(elem, parent); elem=parent; af0035 1999-12-31 Fredrik Hübinette (Hubbe) while(elem && (values[elem] < values[parent=(elem -1)/2])) b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) { SWAP(elem, parent); elem=parent; } adjust_down(elem); return 1; } return 0; } 5b9188 2006-04-24 Robert Hinn //! Push an element onto the heap. The heap will automatically sort itself //! so that the smallest value will be at the top. b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) void push(mixed value) { if(num_values >= sizeof(values)) 4720a6 1999-12-30 Fredrik Hübinette (Hubbe) values+=allocate(10+sizeof(values)/4); b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) values[num_values++]=value; adjust_up(num_values-1); verify_heap(); } 5b9188 2006-04-24 Robert Hinn //! Takes a value in the heap and sorts it through the heap to maintain //! its sort criteria (increasing order). b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) void adjust(mixed value) { int pos=search(values, value); if(pos>=0) if(!adjust_up(pos)) adjust_down(pos); verify_heap(); } 5b9188 2006-04-24 Robert Hinn //! Removes and returns the item on top of the heap, //! which also is the smallest value in the heap. b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) mixed top() { mixed ret; if(!num_values) error("Heap underflow!\n"); ret=values[0]; if(sizeof(values) > 1) { num_values--; values[0]=values[num_values]; values[num_values]=0; adjust_down(0); if(num_values * 3 + 10 < sizeof(values)) values=values[..num_values+10]; } return ret; verify_heap(); } 5b9188 2006-04-24 Robert Hinn //! Returns the number of elements in the heap. b78e3a 1999-12-30 Fredrik Hübinette (Hubbe) int size() { return num_values; } 5b9188 2006-04-24 Robert Hinn //! Returns the item on top of the heap (which is also the smallest value //! in the heap) without removing it. mixed peek() { if (!num_values) return UNDEFINED; return values[0]; }