50094. Word Learning

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int t;
int arr[26][26] = {0};
int used[26][26] = {0};

static inline int map_alpha(char c){
    return c - 'a';
}
static inline int is_valid(int x){
    return x >= 0 && x < 26;
}

void print_arr(){
    for(int i = 0; i < 26; i++){
        for(int j = 0; j < 26; j++){
            printf("%d%c", arr[i][j], j == 25 ? '\n' : ' ');
        }
    }
}

void record(char* s, int n){
    for(int i = 0; i < n - 1; i++){
        int n1 = map_alpha(s[i]);
        int n2 = map_alpha(s[i + 1]);
        if(is_valid(n1) && is_valid(n2)){
            arr[n1][n2]++;
        }
    }
}

void solve(){
    int vis[26] = {0};

    int start_x, start_y, max_cnt = -1;
    for(int i = 0; i < 26; i++){
        for(int j = 0; j < 26; j++){
            if(arr[i][j] > max_cnt){
                start_x = i, start_y = j;
                max_cnt = arr[i][j];
            }
        }
    }

    printf("%c%c", start_x + 'a', start_y + 'a');
    vis[start_x] = 1, vis[start_y] = 1;

    start_x = start_y;
    while(1){
        int max_idx, max_cnt = -1;
        for(int i = 0; i < 26; i++){
            if(arr[start_x][i] > max_cnt && vis[i] == 0){
                max_idx = i;
                max_cnt = arr[start_x][i];
            }
        }

        if(max_cnt <= t) break;

        printf("%c", max_idx + 'a');
        vis[max_idx] = 1;
        start_x = max_idx;
    }
    printf("\n");

}


int main(){
    scanf("%d", &t);
    char line[1024];
    while(fgets(line, 1024, stdin) != NULL){
        int n = strlen(line);
        record(line, n);
    }
    print_arr();
    solve();
}