ADDED   aoc2025.c
Index: aoc2025.c
==================================================================
--- /dev/null
+++ aoc2025.c
@@ -0,0 +1,189 @@
+#include <ctype.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "aocdailies.h"
+#include "aocutils.h"
+
+/* === aoc202503 =======================================================
+===================================================================== */
+static long long unsigned maxj(const unsigned char *b, unsigned blen, unsigned nlen) {
+    if (nlen == 0) return 0;
+    const unsigned char *newb = b + 1;
+    unsigned newlen = blen - 1;
+    unsigned localmax = 0;
+    for (unsigned k = 0; k < blen - nlen + 1; k++) {
+        if (b[k] > localmax) {
+            localmax = b[k];
+            newb = b + k + 1;
+            newlen = blen - k - 1;
+        }
+    }
+    return localmax*upow(10, nlen - 1) + maxj(newb, newlen, nlen - 1);
+}
+
+void aoc202503(char *data, size_t len) {
+    (void)len; // unused argument
+    long long unsigned part1 = 0, part2 = 0;
+    char *p = data;
+    for (;;) {
+        char *pp = strchr(p, '\n');
+        if (pp == NULL) break;
+        unsigned char bank[256] = {0};
+        unsigned banklen;
+        for (banklen = 0; banklen < (unsigned)(pp - p); banklen++) {
+            bank[banklen] = (unsigned)p[banklen] - '0';
+        }
+        part1 += maxj(bank, banklen, 2);
+        part2 += maxj(bank, banklen, 12);
+        p = pp + 1;
+    }
+    printf("parts 1 and 2: %llu %llu\n", part1, part2);
+}
+
+/* === aoc202502 =======================================================
+===================================================================== */
+static int extractdata(char **data, char *p1, char *p2) {
+    char *d = *data;
+    if (*d == ',') d++; // skip ','
+    if (!isdigit(*d)) return 0;
+    while (isdigit(*d)) { *p1++ = *d++; *p1 = 0; }
+    if (*d != '-') { fprintf(stderr, "bad data\n"); exit(EXIT_FAILURE); }
+    d++; // skip '-'
+    while (isdigit(*d)) { *p2++ = *d++; *p2 = 0; }
+    *data = d;
+    return 1;
+}
+
+static int prepeat(int n, long long unsigned v) {
+    char tmp[42];
+    int len = sprintf(tmp, "%llu", v);
+    if (len % n) return 0;
+    if (len < 2*n) return 0;
+    for (int k = 0; k+n < len; k++) {
+        if (tmp[k] != tmp[k+n]) return 0;
+    }
+    return 1;
+}
+
+static long long unsigned suminvalid2(const char *start, const char *finis) {
+    long long unsigned retval = 0;
+    long long unsigned pstart = 0, pfinis = 0;
+    int k = 0;
+    while (start[k]) {
+        pstart *= 10; pstart += (unsigned)start[k] - '0';
+        k++;
+    }
+    k = 0;
+    while (finis[k]) {
+        pfinis *= 10; pfinis += (unsigned)finis[k] - '0';
+        k++;
+    }
+    for (long long unsigned kk = pstart; kk <= pfinis; kk++) {
+        if (prepeat(1, kk)) retval += kk;
+        else if (prepeat(2, kk)) retval += kk;
+        else if (prepeat(3, kk)) retval += kk;
+        else if (prepeat(4, kk)) retval += kk;
+        else if (prepeat(5, kk)) retval += kk;
+        else if (prepeat(6, kk)) retval += kk;
+        else if (prepeat(7, kk)) retval += kk;
+        else if (prepeat(8, kk)) retval += kk;
+        else if (prepeat(9, kk)) retval += kk;
+    }
+    return retval;
+}
+
+static long long unsigned suminvalid(const char *start, const char *finis) {
+    long long unsigned pstart = 0, pfinis = 0;
+    int k = 0;
+    while (start[k]) {
+        pstart *= 10; pstart += (unsigned)start[k] - '0';
+        pfinis *= 10; pfinis += (unsigned)finis[k] - '0';
+        k++;
+    }
+    long long unsigned lo = pstart / upow(10, (unsigned)(k/2));
+    long long unsigned hi = pfinis / upow(10, (unsigned)(k/2));
+    long long unsigned retval = 0;
+    for (long long unsigned kk = lo; kk <= hi; kk++) {
+        long long unsigned val = kk*upow(10, (unsigned)(k/2)) + kk;
+        if ((pstart <= val) && (val <= pfinis)) retval += val;
+    }
+    return retval;
+}
+
+void aoc202502(char *data, size_t len) {
+    (void)len; // unused argument
+    long long unsigned part1 = 0;
+    long long unsigned part2 = 0;
+    char start[42], finis[42];
+    while (extractdata(&data, start, finis)) {
+        int lenstart = strlen(start);
+        int lenfinis = strlen(finis);
+        part2 += suminvalid2(start, finis);
+        if (lenstart != lenfinis) {
+            char tmp[42];
+            if (lenfinis % 2) {
+                sprintf(tmp, "%llu", upow(10, (unsigned)lenstart) - 1);
+                part1 += suminvalid(start, tmp);
+            } else {
+                sprintf(tmp, "%llu", upow(10, (unsigned)lenstart));
+                part1 += suminvalid(tmp, finis);
+            }
+        } else {
+            if (lenstart % 2) {
+                part1 += 0;
+            } else {
+                part1 += suminvalid(start, finis);
+            }
+        }
+    }
+    printf("parts 1 and 2: %llu %llu\n", part1, part2);
+}
+
+/* === aoc202501 =======================================================
+===================================================================== */
+static int zeroaccum(int start, char d, int v, int *p1, int *p2) {
+    int direction;
+    switch (d) {
+        default: fprintf(stderr, "Invalid letter: %c\n", d);
+                 exit(EXIT_FAILURE);
+        case 'R': direction = 1;
+                  break;
+        case 'L': direction = -1;
+                  break;
+    }
+    while (v--) {
+        start += direction;
+        if (start == -1) start = 99;
+        if (start == 100) start = 0;
+        if (start == 0) *p2 += 1;
+    }
+    if (start == 0) *p1 += 1;
+    return start;
+}
+
+void aoc202501(char *data, size_t len) {
+    (void)len; // unused argument
+    int pos = 50;
+    int part1 = 0, part2 = 0;
+    char dir; int value;
+    while (*data) {
+        dir = *data++;
+        value = 0;
+        while (isdigit(*data)) {
+            value *= 10;
+            value += *data - '0';
+            data++;
+        }
+        while (isspace(*data)) data++; // skip whitespace
+        pos = zeroaccum(pos, dir, value, &part1, &part2);
+    }
+
+    // part1
+    printf("password for part1 is %d\n", part1);
+
+    // part2
+    printf("password for part2 is %d\n", part2);
+}