gistfile1.c

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

#define MAX(x, y) (((x) > (y)) ? (x) : (y))

int main(void)
{
    static char input[] = "FourscoreandsevenyearsagoourfaathersbroughtforthonthiscontainentanewnationconceivedinzLibertyanddedicatedtothepropositionthatallmenarecreatedequalNowweareengagedinagreahtcivilwartestingwhetherthatnaptionoranynartionsoconceivedandsodedicatedcanlongendureWeareqmetonagreatbattlefiemldoftzhatwarWehavecometodedicpateaportionofthatfieldasafinalrestingplaceforthosewhoheregavetheirlivesthatthatnationmightliveItisaltogetherfangandproperthatweshoulddothisButinalargersensewecannotdedicatewecannotconsecratewecannothallowthisgroundThebravelmenlivinganddeadwhostruggledherehaveconsecrateditfaraboveourpoorponwertoaddordetractTgheworldadswfilllittlenotlenorlongrememberwhatwesayherebutitcanneverforgetwhattheydidhereItisforusthelivingrathertobededicatedheretotheulnfinishedworkwhichtheywhofoughtherehavethusfarsonoblyadvancedItisratherforustobeherededicatedtothegreattdafskremainingbeforeusthatfromthesehonoreddeadwetakeincreaseddevotiontothatcauseforwhichtheygavethelastpfullmeasureofdevotionthatweherehighlyresolvethatthesedeadshallnothavediedinvainthatthisnationunsderGodshallhaveanewbirthoffreedomandthatgovernmentofthepeoplebythepeopleforthepeopleshallnotperishfromtheearth";

    int i, best_idx;
    static const int n = sizeof input;
    int *palin_lens = malloc((sizeof palin_lens[0]) * n);
    for (i = 0; i < n; ++i) {
        palin_lens[i] = 1;
    }
    for (i = 0; i < n; ++i) {
        if (((i - 1) < 0) || ((i + palin_lens[i]) >= n)) {
            continue;
        }

        if (input[i - 1] == input[i + palin_lens[i]]) {
            if (palin_lens[i] + 2 > palin_lens[i - 1]) {
                palin_lens[i - 1] = palin_lens[i] + 2;
                i = 0;
            }
        }
    }
    best_idx = -1;
    for (i = 0; i < n; ++i) {
        if (best_idx < 0 || palin_lens[i] > palin_lens[best_idx]) {
            best_idx = i;
        }
    }
    input[best_idx + palin_lens[best_idx]] = '\0';
    printf("%s\n", &input[best_idx]);
    return 0;
}