idz2_8

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

void solve(char * s, long long n, FILE *output) {
    char * p1 = NULL, * p2 = s + n;
    if (n == 1) {
        p1 = s;
    }
    for (long long i = n - 1; i >= 1; --i) {
        if (s[i - 1] < s[i]) {
            p1 = s + i - 1;
        } else {
            if (p1 != NULL) {
                break;
            }
            p2 = s + i;
        }
    }
    if (p1 != NULL) {
        long long i = 0;
        if (output == stdin) {
            while (p1 + i != p2) {
                printf("%c", *(p1 + i));
                i++;
            }
        } else {
            while (p1 + i != p2) {
                fprintf(stdin, "%c", *(p1 + i));
                i++;
            }
        }

    }
}

void generate_string(char * s, long long n) {
    for (int i = 0; i < n; ++i) {
        char tmp = rand() % 127 + 1;
        s[i] = tmp;
    }
}

int main(int argc, char **argv) {
    char * s;
    long long n;
    if (strcmp(argv[1], "-r") == 0) {
        srand(time(0));
        n = rand() % 2001;
        s = (char *)malloc((n + 1) * sizeof(char));
        generate_string(s, n);
        clock_t begin = clock();
        solve(s, n, stdin);
        clock_t end = clock();
        double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
        printf("\nProgram execution time: %lf\n", time_spent);
    } else if (strcmp(argv[1], "-c") == 0) {
        scanf("%lld", &n);
        getchar();
        s = (char *)malloc((n + 1) * sizeof(char));
        fgets(s, n + 1, stdin);
        clock_t begin = clock();
        solve(s, n, stdin);
        clock_t end = clock();
        double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
        printf("Program execution time: %lf", time_spent);
    } else if (strcmp(argv[1], "-f") == 0) {
        FILE *input, *output;
        input = fopen(argv[2], "r");
        output = fopen(argv[3], "w");
        fscanf(input, "%lld", &n);
        s = (char *)malloc((n + 1) * sizeof(char));
        fgetc(input);
        fgets(s, n + 1, input);
        clock_t begin = clock();
        solve(s, n, output);
        clock_t end = clock();
        double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
        printf("Program execution time: %lf", time_spent);
        fclose(input);
        fclose(output);
    }
    return 0;
}