| /*@ Extern Coq | |
| (Forall : {A} -> (A -> Prop) -> list A -> Prop) | |
| (Z::le : Z -> Z -> Prop) | |
| (Z::ge : Z -> Z -> Prop) | |
| (HuffmanOptimalCost : list Z -> Z -> Prop) | |
| */ | |
| /*@ Import Coq Require Import PVbench.Algorithms.huffman_encoding.rocq.spec_lib */ | |
| int huffman_cost(int *weights, int n) | |
| /*@ With (weights_l : list Z) | |
| Require | |
| 1 <= n && n <= 8 && | |
| Zlength(weights_l) == n && | |
| Forall(Z::le(1), weights_l) && Forall(Z::ge(1000), weights_l) && | |
| IntArray::full(weights, n, weights_l) | |
| Ensure | |
| HuffmanOptimalCost(weights_l, __return) && | |
| IntArray::full(weights, n, weights_l) | |
| */ | |
| { | |
| int work[8]; | |
| for (int i = 0; i < n; ++i) { | |
| work[i] = weights[i]; | |
| } | |
| int active = n; | |
| int total = 0; | |
| while (active > 1) { | |
| int first = 0; | |
| for (int i = 1; i < active; ++i) { | |
| if (work[i] < work[first]) { | |
| first = i; | |
| } | |
| } | |
| int x = work[first]; | |
| --active; | |
| work[first] = work[active]; | |
| int second = 0; | |
| for (int i = 1; i < active; ++i) { | |
| if (work[i] < work[second]) { | |
| second = i; | |
| } | |
| } | |
| int y = work[second]; | |
| --active; | |
| work[second] = work[active]; | |
| int merged = x + y; | |
| total += merged; | |
| work[active] = merged; | |
| ++active; | |
| } | |
| return total; | |
| } | |