Accepted implementation for the problem 1321C in codeforces

codeforces-1321C.c

/*
 * =====================================================================================
 *
 *       Filename:  1321C.cpp
 *
 *    Description:  codeforces 1321C. Remove Adjacent
 *
 *        Version:  1.0
 *        Created:  2020年03月12日
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  lionking
 *   Organization:  None
 *
 * =====================================================================================
 */
#include <stdio.h>
#define MAX_S 128

int main()
{
    int len, idx = 0, result = 0;
    char s[2][MAX_S] = {"", ""};

    scanf("%d\n", &len);
    fgets(s[idx]+1, MAX_S, stdin);

    for (char c = 'z'; c >= 'a'; ) {
        for (int i = 1; i <= len; ++i) {
            if (s[idx][i] != c) { continue; }
            if ((c - s[idx][i-1] == 1) || (c - s[idx][i+1] == 1)) {
                s[idx][i] = 0;
            }
        }
        int new_len = 0;
        for (int i = 1; i <= len; ++i) {
            if (s[idx][i] == 0) { continue; }
            s[idx ^ 1][++new_len] = s[idx][i];
        }

        if (new_len == len) { --c; }
        else { result += len - new_len; }
        len = new_len;
        idx ^= 1;
    }
    printf("%d\n", result);

    return 0;
}