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SmallestChange.java
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SmallestChange.java
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/*
* Title: Smallest Change
*
* Given an input amount of change x, write a function to determine the
* minimum number of coins required to make that amount of change.
* Execution: javac SmallestChange.java && java SmallestChange
* For more details, check out http://www.byte-by-byte.com/smallestchange
*/
public class SmallestChange {
public static int change(int x, int[] coins) {
if (x == 0) {
return 0;
}
int min = x;
for (int coin : coins) {
if (x - coin >= 0) {
int c = change(x - coin, coins);
if (min > c + 1) {
min = c + 1;
}
}
}
return min;
}
public static int changeDynamic(int x, int[] coins) {
int[] cache = new int[x];
for (int i = 1; i < x; i++) {
cache[i] = -1;
}
return changeDynamic(x, coins, cache);
}
public static int changeDynamic(int x, int[] coins, int[] cache) {
if (x == 0) {
return 0;
}
int min = x;
for (int coin : coins) {
if (x - coin >= 0) {
int c;
if (cache[x - coin] >= 0) {
c = cache[x - coin];
} else {
c = changeDynamic(x - coin, coins, cache);
cache[x - coin] = c;
}
if (min > c + 1) {
min = c + 1;
}
}
}
return min;
}
// Sample test cases
public static void main(String[] args) {
int[] coins = new int[]{1, 5, 10, 25};
// Tests for change:
assert change(1, coins) == 1:
"Smallest from 1 is 1";
assert change(3, coins) == 3:
"Smallest from 3 is 3";
assert change(7, coins) == 3:
"Smallest from 7 is 3";
assert change(32, coins) == 4:
"Smallest from 32 is 4";
// Tests for changeDynamic:
assert changeDynamic(1, coins) == 1:
"Smallest from 1 is 1";
assert changeDynamic(3, coins) == 3:
"Smallest from 3 is 3";
assert changeDynamic(7, coins) == 3:
"Smallest from 7 is 3";
assert changeDynamic(32, coins) == 4:
"Smallest from 32 is 4";
System.out.println("Passed all test cases");
}
}