51 lines
1.5 KiB
Dart
51 lines
1.5 KiB
Dart
/**
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* File: coin_change_greedy.dart
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* Created Time: 2023-08-11
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* Author: liuyuxin (gvenusleo@gmail.com)
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*/
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/* Coin change: Greedy */
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int coinChangeGreedy(List<int> coins, int amt) {
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// Assume coins list is ordered
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int i = coins.length - 1;
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int count = 0;
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// Loop for greedy selection until no remaining amount
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while (amt > 0) {
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// Find the smallest coin close to and less than the remaining amount
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while (i > 0 && coins[i] > amt) {
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i--;
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}
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// Choose coins[i]
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amt -= coins[i];
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count++;
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}
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// If no feasible solution is found, return -1
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return amt == 0 ? count : -1;
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}
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/* Driver Code */
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void main() {
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// Greedy: can ensure finding a global optimal solution
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List<int> coins = [1, 5, 10, 20, 50, 100];
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int amt = 186;
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int res = coinChangeGreedy(coins, amt);
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print("\ncoins = $coins, amt = $amt");
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print("Minimum number of coins required to make up $amt = $res");
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// Greedy: cannot ensure finding a global optimal solution
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coins = [1, 20, 50];
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amt = 60;
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res = coinChangeGreedy(coins, amt);
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print("\ncoins = $coins, amt = $amt");
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print("Minimum number of coins required to make up $amt = $res");
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print("In reality, the minimum number needed is 3, i.e., 20 + 20 + 20");
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// Greedy: cannot ensure finding a global optimal solution
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coins = [1, 49, 50];
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amt = 98;
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res = coinChangeGreedy(coins, amt);
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print("\ncoins = $coins, amt = $amt");
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print("Minimum number of coins required to make up $amt = $res");
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print("In reality, the minimum number needed is 2, i.e., 49 + 49");
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}
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