CoinChange
CoinChange.java 源码
package algorithm.dp;
import java.util.Arrays;
/**
* @author roseduan
* @description 零钱兑换
*/
public class CoinChange {
/**
* 回溯的方法，列举有所的可能，并求得最小值
* 执行会超时
*/
public int coinChange1(int[] coins, int amount) {
helper(coins, 0, amount);
return min == Integer.MAX_VALUE ? -1 : min;
}
private int min = Integer.MAX_VALUE;
private void helper(int[] coins, int count, int amount) {
if (amount <= 0) {
if (amount == 0 && count < min) {
min = count;
}
return;
}
for (int n : coins) {
helper(coins, count + 1, amount - n);
}
}
/**
* 动态规划的方式
*/
public int coinChange2(int[] coins, int amount) {
int[] dp = new int[amount + 1];
Arrays.fill(dp, amount + 1);
dp[0] = 0;
for (int i = 1; i <= amount; i++) {
for (int n : coins) {
if (i >= n) {
dp[i] = Math.min(dp[i], dp[i - n] + 1);
}
}
}
return dp[amount] > amount ? -1 : dp[amount];
}
}
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