Data commit

Task/Next-highest-int-from-digits/C/next-highest-int-from-digits.c

@@ -0,0 +1,55 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+void swap(char* str, int i, int j) {
+    char c = str[i];
+    str[i] = str[j];
+    str[j] = c;
+}
+
+void reverse(char* str, int i, int j) {
+    for (; i < j; ++i, --j)
+        swap(str, i, j);
+}
+
+bool next_permutation(char* str) {
+    int len = strlen(str);
+    if (len < 2)
+        return false;
+    for (int i = len - 1; i > 0; ) {
+        int j = i, k;
+        if (str[--i] < str[j]) {
+            k = len;
+            while (str[i] >= str[--k]) {}
+            swap(str, i, k);
+            reverse(str, j, len - 1);
+            return true;
+        }
+    }
+    return false;
+}
+
+uint32_t next_highest_int(uint32_t n) {
+    char str[16];
+    snprintf(str, sizeof(str), "%u", n);
+    if (!next_permutation(str))
+        return 0;
+    return strtoul(str, 0, 10);
+}
+
+int main() {
+    uint32_t numbers[] = {0, 9, 12, 21, 12453, 738440, 45072010, 95322020};
+    const int count = sizeof(numbers)/sizeof(int);
+    for (int i = 0; i < count; ++i)
+        printf("%d -> %d\n", numbers[i], next_highest_int(numbers[i]));
+    // Last one is too large to convert to an integer
+    const char big[] = "9589776899767587796600";
+    char next[sizeof(big)];
+    memcpy(next, big, sizeof(big));
+    next_permutation(next);
+    printf("%s -> %s\n", big, next);
+    return 0;
+}