BiruLyu
7/5/2017 - 5:43 PM

## #Iterative Method:#.java

``````/*
[1,5,10,20,25] 40
Greedy Approach: 40 = 25 + 10 + 5
Expected Answer: 40 = 20 + 20
*/

public class Solution {
int total = Integer.MAX_VALUE;

public int coinChange(int[] coins, int amount) {
if (amount == 0) {
return 0;
}
Arrays.sort(coins);

count(amount, coins.length - 1, coins, 0);
}

private void count(int amount, int index, int[] coins, int count) {
if (index < 0 ) {
return;
}

int c = amount / coins[index];
for (int i = c; i >= 0; i--) {
int newCount = count + i;
int rem = amount - i * coins[index];

if (rem == 0) {
total = Math.min(total, newCount);
} else {
if (newCount >= total - 1) {
break;
} else {
count(rem, index - 1, coins, newCount);
}
}
}
}
}``````
``````/*
[1,5,10,20,25] 40
Greedy Approach: 40 = 25 + 10 + 5
Expected Answer: 40 = 20 + 20
*/

public class Solution {
public int coinChange(int[] coins, int amount) {
if (amount < 1) return 0;
int[] dp = new int[amount + 1];
int len = coins.length;
Arrays.fill(dp, amount + 1);
dp[0] = 0;
for (int i = 1; i <= amount; i++) {
for (int j = 0; j < len; j++) {
if (coins[j] <= i) {
dp[i] = Math.min(dp[i], dp[i - coins[j]] + 1);
}
}
}
return dp[amount] > amount ? -1 : dp[amount];

}

}

``````
``````public class Solution {
public int coinChange(int[] coins, int amount) {
if(amount<1) return 0;
return helper(coins, amount, new int[amount]);
}

private int helper(int[] coins, int rem, int[] count) { // rem: remaining coins after the last step; count[rem]: minimum number of coins to sum up to rem
if(rem<0) return -1; // not valid
if(rem==0) return 0; // completed
if(count[rem-1] != 0) return count[rem-1]; // already computed, so reuse
int min = Integer.MAX_VALUE;
for(int coin : coins) {
int res = helper(coins, rem-coin, count);
if(res>=0 && res < min)
min = 1+res;
}
count[rem-1] = (min==Integer.MAX_VALUE) ? -1 : min;
return count[rem-1];
}
}``````
``````public class Solution {
public int coinChange(int[] coins, int amount) {
if(amount<1) return 0;
int[] dp = new int[amount+1];
int sum = 0;

while(++sum<=amount) {
int min = -1;
for(int coin : coins) {
if(sum >= coin && dp[sum-coin]!=-1) {
int temp = dp[sum-coin]+1;
min = min<0 ? temp : (temp < min ? temp : min);
}
}
dp[sum] = min;
}
return dp[amount];
}
}``````