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LC322_coin_change.java
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66 lines (60 loc) · 1.76 KB
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package Week06;
import java.util.*;
public class LC322_coin_change {
/*
* 动态规划：自下而上
a.分治（子问题）:前面能转移过来的状态的最小值加上枚举的硬币数量 1
b.状态数组定义 : 定义 F(i) 为组成金额 i 所需最少的硬币数量
c.DP方程: F(i)=min(F(i−1),F(i−2),F(i−5))+1
初始值：F(0)=0
* */
public int coinChange(int[] coins, int amount) {
int a = amount+1;
int[] dp = new int[amount+1];
Arrays.fill(dp,a);
dp[0] =0;
for (int remainAmt=1;remainAmt<=amount;remainAmt++){
for(int c :coins){
if (c<=remainAmt){
dp[remainAmt] = Math.min(dp[remainAmt],dp[remainAmt-c]+1);
}
}
}
return dp[amount]==a ? -1: dp[amount];
}
/*
* BFS:找到叶节点为0的最短路径
* 超出内存限制,这也是一种暴力递归
* */
public int coinChange_BFS(int[] coins, int amount) {
Queue<Integer> queue = new ArrayDeque<>();
queue.offer(amount);
int level =0;
while (!queue.isEmpty()){
int size = queue.size();
for (int i=0;i<size;i++){
Integer amt = queue.poll();
if (amt == 0){
return level;
}
else if (amt <0){
continue;
}
else{
for (Integer c : coins){
queue.offer(amt-c);
}
}
}
level++;
}
return -1;
}
}
class Test36{
public static void main(String[] args) {
LC322_coin_change s = new LC322_coin_change();
int[] coins = {1,2,5};
s.coinChange(coins,100);
}
}