g2201_2300.s2262_total_appeal_of_a_string.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g2201_2300.s2262_total_appeal_of_a_string;

// #Hard #String #Hash_Table #Dynamic_Programming
// #2022_06_15_Time_6_ms_(97.92%)_Space_48.3_MB_(80.72%)

import java.util.Arrays;

/**
 * 2262 - Total Appeal of A String\.
 *
 * Hard
 *
 * The **appeal** of a string is the number of **distinct** characters found in the string.
 *
 * *   For example, the appeal of `"abbca"` is `3` because it has `3` distinct characters: `'a'`, `'b'`, and `'c'`.
 *
 * Given a string `s`, return _the **total appeal of all of its **substrings**.**_
 *
 * A **substring** is a contiguous sequence of characters within a string.
 *
 * **Example 1:**
 *
 * **Input:** s = "abbca"
 *
 * **Output:** 28
 *
 * **Explanation:** The following are the substrings of "abbca":
 *
 * - Substrings of length 1: "a", "b", "b", "c", "a" have an appeal of 1, 1, 1, 1, and 1 respectively. The sum is 5.
 *
 * - Substrings of length 2: "ab", "bb", "bc", "ca" have an appeal of 2, 1, 2, and 2 respectively. The sum is 7.
 *
 * - Substrings of length 3: "abb", "bbc", "bca" have an appeal of 2, 2, and 3 respectively. The sum is 7.
 *
 * - Substrings of length 4: "abbc", "bbca" have an appeal of 3 and 3 respectively. The sum is 6.
 *
 * - Substrings of length 5: "abbca" has an appeal of 3. The sum is 3.
 *
 * The total sum is 5 + 7 + 7 + 6 + 3 = 28. 
 *
 * **Example 2:**
 *
 * **Input:** s = "code"
 *
 * **Output:** 20
 *
 * **Explanation:** The following are the substrings of "code":
 *
 * - Substrings of length 1: "c", "o", "d", "e" have an appeal of 1, 1, 1, and 1 respectively. The sum is 4.
 *
 * - Substrings of length 2: "co", "od", "de" have an appeal of 2, 2, and 2 respectively. The sum is 6.
 *
 * - Substrings of length 3: "cod", "ode" have an appeal of 3 and 3 respectively. The sum is 6.
 *
 * - Substrings of length 4: "code" has an appeal of 4. The sum is 4.
 *
 * The total sum is 4 + 6 + 6 + 4 = 20. 
 *
 * **Constraints:**
 *
 * *   1 <= s.length <= 10⁵
 * *   `s` consists of lowercase English letters.
**/
public class Solution {
    public long appealSum(String s) {
        int len = s.length();
        int[] lastPos = new int[26];
        Arrays.fill(lastPos, -1);
        long res = 0;
        for (int i = 0; i < len; i++) {
            int idx = s.charAt(i) - 'a';
            res += (i - lastPos[idx]) * (len - i);
            lastPos[idx] = i;
        }
        return res;
    }
}