## Overview

PAT Advanced 1092 To Buy or Not to Buy: use HashMap to keep the character counts, calculate the difference to check if the shop has extra or insufficient beads.

For the sake of simplicity, let’s use the characters in the ranges [0-9], [a-z], and [A-Z] to represent the colors. For example, the 3rd string in Figure 1 is the one that Eva would like to make. Then the 1st string is okay since it contains all the necessary beads with 8 extra ones; yet the 2nd one is not since there is no black bead and one less red bead.

Figure 1

Input Specification:

Each input file contains one test case. Each case gives in two lines the strings of no more than 1000 beads which belong to the shop owner and Eva, respectively.

Output Specification:

For each test case, print your answer in one line. If the answer is “Yes”, then also output the number of extra beads Eva has to buy; or if the answer is “No”, then also output the number of beads missing from the string. There must be exactly 1 space between the answer and the number.

Sample Input 1:

```ppRYYGrrYBR2258
YrR8RrY```

Sample Output 1:

`Yes 8`

Sample Input 2:

```ppRYYGrrYB225
YrR8RrY```

Sample Output 1:

`No 2`

## Solution: HashMap

The following Java code just implement the ideas described:  use HashMap to keep the character counts, calculate the difference to check if the shop has extra or insufficient beads. And it is accepted by the PAT OJ:

```import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

/**
* @author Sigmainfy
*/

public class Main {

private static Map<Character, Integer> getCountingMap(final String s) {
Map<Character, Integer> counts = new HashMap<Character, Integer>();

for (int i = 0, len = s.length(); i < len; ++i) {
Character curr = s.charAt(i);
if (counts.get(curr) == null) {
counts.put(curr, 1);
} else {
counts.put(curr, counts.get(curr) + 1);
}
}

return counts;
}

// how many counts are missing in existed
private static int getMissingCounts(final Map<Character, Integer> existedCounts, final Map<Character, Integer> requireCounts) {
int missingCount = 0;
// missing
for (Map.Entry<Character, Integer> entry : requireCounts.entrySet()) {
Character c = entry.getKey();
Integer require = entry.getValue();
Integer existed = existedCounts.get(c);
if (existed == null) {
existed = 0;
}
missingCount += (existed >= require ? 0 : require - existed);
}
return missingCount;
}

public static void main(String [] args) {
Scanner scanner = new Scanner(System.in);

Map<Character, Integer> existedCounts = getCountingMap(scanner.next());
Map<Character, Integer> requireCounts = getCountingMap(scanner.next());

int missingCount = getMissingCounts(existedCounts, requireCounts);

if (missingCount > 0) {
System.out.println("No " + missingCount);
} else {
System.out.println("Yes " + getMissingCounts(requireCounts, existedCounts));
}

scanner.close();
return ;
}
}
```

## Summary

PAT Advanced 1092 To Buy or Not to Buy: use HashMap to keep the character counts, calculate the difference to check if the shop has extra or insufficient beads.

Written on May 23, 2015