Longest Happy String

class Solution {
public:
    string generateLongestDiverseString(int aCount, int bCount, int cCount) {
        int aStreak = 0, bStreak = 0, cStreak = 0;
        int maxLen = aCount + bCount + cCount;
        string result = "";

        for (int i = 0; i < maxLen; i++) {
            if ((aCount >= bCount && aCount >= cCount && aStreak != 2) ||
                (aCount > 0 && (bStreak == 2 || cStreak == 2))) {
                result += 'a';
                aCount--;
                aStreak++;
                bStreak = 0;
                cStreak = 0;
            } else if ((bCount >= aCount && bCount >= cCount && bStreak != 2) ||
                       (bCount > 0 && (cStreak == 2 || aStreak == 2))) {
                result += 'b';
                bCount--;
                bStreak++;
                aStreak = 0;
                cStreak = 0;
            } else if ((cCount >= aCount && cCount >= bCount && cStreak != 2) ||
                       (cCount > 0 and (aStreak == 2 || bStreak == 2))) {
                result += 'c';
                cCount--;
                cStreak++;
                aStreak = 0;
                bStreak = 0;
            }
        }
        return result;
    }
};

The provided C++ solution tackles the problem of generating the longest string using the characters 'a', 'b', and 'c', such that no three consecutive characters are the same. Here's how the solution approaches the issue:

• It starts by initializing counters for the streaks of each character (aStreak, bStreak, cStreak) and their respective counts (aCount, bCount, cCount).
• The function's primary loop runs through the total number of characters available (maxLen), determined by summing aCount, bCount, and cCount.
• Inside the loop, the solution decides which character to append next based on:
  • The counts of each character relative to the others, ensuring the most frequent character is used unless it would form three consecutive same characters.
  • The streaks of other characters, to avoid having three consecutive occurrences of any character.
• After selecting a character, it updates the respective character's count and reset the streaks for the other characters to zero while incrementing the streak of the chosen character.
• This approach strategically balances the characters, using the highest available character count without violating the consecutive character condition, effectively creating the longest diverse string possible.

This solution ensures no conditions like 'aaa', 'bbb', or 'ccc', develop, harnessing checks and balances via streak and count, to construct the string with the necessary constraints.

class Solution {

    public String generateLongestString(int x, int y, int z) {
        int countX = 0, countY = 0, countZ = 0;
        int totalLoops = x + y + z;
        StringBuilder result = new StringBuilder();

        for (int i = 0; i < totalLoops; i++) {
            if (
                (x >= y && x >= z && countX != 2) ||
                (x > 0 && (countY == 2 || countZ == 2))
            ) {
                result.append('a');
                x--;
                countX++;
                countY = 0;
                countZ = 0;
            } else if (
                (y >= x && y >= z && countY != 2) ||
                (y > 0 && (countZ == 2 || countX == 2))
            ) {
                result.append('b');
                y--;
                countY++;
                countX = 0;
                countZ = 0;
            } else if (
                (z >= x && z >= y && countZ != 2) ||
                (z > 0 && (countX == 2 || countY == 2))
            ) {
                result.append('c');
                z--;
                countZ++;
                countX = 0;
                countY = 0;
            }
        }
        return result.toString();
    }
}

The Java method generateLongestString provided in the code constructs the "longest happy string" based on the input values of x, y, and z. These values represent the maximum possible counts of 'a', 'b', and 'c' respectively. A string is considered "happy" if no three consecutive characters are the same.

• The method initializes counters for 'a' (countX), 'b' (countY), and 'c' (countZ), all set to zero.
• It also calculates the total number of loops required using the sum of x, y, and z.
• A StringBuilder object result accumulates the resultant string.

In the loop, the method follows these rules to append the correct character:

1. Append 'a' if either x is the largest number among x, y, and z not having reached 2 consecutive 'a's, or if 'b' or 'c' has reached 2 consecutive additions.
   • After appending 'a', decrement x, increment countX and reset countY and countZ to zero.
2. Append 'b' under similar conditions: if y is the highest count or if appending 'b' would prevent three consecutive occurrences of 'a' or 'c'.
   • On appending 'b', similarly manage y, countY, countX, and countZ.
3. Append 'c' if z is either the highest or to prevent a triad of consecutive 'a' or 'b'.
   • Adjust z, countZ, countX, and countY accordingly.

The loop continues until all characters declared by x, y, and z are exhausted, following which the result is converted to string format and returned. This method assures the generation of the longest sequence under the constraints provided, ensuring optimal character use without violating the "happy" condition.

class Solution:
    def generateString(self, x: int, y: int, z: int) -> str:
        streakA, streakB, streakC = 0, 0, 0
        iterations = x + y + z
        output = []

        for _ in range(iterations):
            if (x >= y and x >= z and streakA != 2) or (x > 0 and (streakB == 2 or streakC == 2)):
                output.append("a")
                x -= 1
                streakA += 1
                streakB = 0
                streakC = 0
            elif (y >= x and y >= z and streakB != 2) or (y > 0 and (streakC == 2 or streakA == 2)):
                output.append("b")
                y -= 1
                streakB += 1
                streakA = 0
                streakC = 0
            elif (z >= x and z >= y and streakC != 2) or (z > 0 and (streakA == 2 or streakB == 2)):
                output.append("c")
                z -= 1
                streakC += 1
                streakA = 0
                streakB = 0

        return "".join(output)

This Python solution focuses on generating the longest string where no three consecutive characters are the same, given counts of 'a's, 'b's, and 'c's. The solution involves the following steps:

1. Initialize counters for streaks of 'a', 'b', and 'c' to track consecutive appearances.

2. Calculate the total number of iterations, which equals the sum of 'a', 'b', and 'c'.

3. Loop through each iteration to build the string:

   • Choose 'a' if 'a' has the highest count among the remaining letters and its streak is less than 2, or if a reduction is needed to prevent a streak of 3 in 'b' or 'c'.
   • Choose 'b' if 'b' has the highest count among the remaining letters and its streak is less than 2, or if a reduction is needed to prevent a streak of 3 in 'a' or 'c'.
   • Choose 'c' similarly based on the remaining count and current streaks of 'a' and 'b'.
   • After appending a character, update the relevant streaks and reset others to zero.

4. The function finally joins the list into a string which represents the longest happy string without three consecutive similar characters.

This approach ensures the most balanced usage of 'a's, 'b's, and 'c's based on their provided counts while adhering to the conditions of the problem prompt, resulting in an efficient solution to generate the desired string.