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135 lines
2.4 KiB
135 lines
2.4 KiB
#include <stddef.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <stdio.h>
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#define pure __attribute__((pure))
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#define pure_const __attribute__((const))
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#define _cold __attribute__((cold, noinline))
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#define noreturn __attribute__((noreturn)) void
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#ifdef DEBUG
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#define dlog(...) fprintf(stderr, "[debug]" __VA_ARGS__)
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#else
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inline extern void do_nothing(int _n, ...) {}
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#define dlog(...) do { if(0) { do_nothing(0 __VA_OPT__(,) __VA_ARGS__); } } while(0)
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#endif
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noreturn static _cold panic(const char* msg)
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{
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fputs(msg, stderr);
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fputc('\n', stderr);
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abort();
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}
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typedef struct sloc {
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int row;
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int column;
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int id;
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} seat_t;
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static const char* input[] = {
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#ifdef TEST
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#include "input-test.h"
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#else
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#include "input.h"
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#endif
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};
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#define input_sz (sizeof(input) / sizeof(char*))
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#define ROW_MAX 128
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#define COL_MAX 8
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inline static void seat_calc_id(seat_t* restrict s)
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{
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s->id = (s->row * 8) + s->column;
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}
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static pure int sbsearch(const char* direct, size_t len, int max)
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{
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int min = 0;
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#define diff (1 + (max - min))
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for(size_t i=0;i<len;i++)
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{
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dlog("%c: min = %d, max = %d\n", direct[i], min, max);
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switch(direct[i])
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{
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case 0:
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panic("string overflow");
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// lower half
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case 'F':
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case 'L':
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max -= diff / 2;
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if(diff==1) return min;
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break;
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// upper half
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case 'R':
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case 'B':
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min += diff / 2;
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if(diff==1) return max;
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break;
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}
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}
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panic("bsearch failed");
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#undef diff
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}
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static pure seat_t pbsearch(const char* str)
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{
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seat_t seat = {
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.row = (int)sbsearch(str, 7, ROW_MAX-1),
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.column = (int)sbsearch(str+7, 3, COL_MAX-1),
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};
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seat_calc_id(&seat);
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return seat;
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}
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#ifdef PART2
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static pure int _seat_cmp(const void* ptr, const void* ptr2)
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{
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const seat_t *s1 = ptr;
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const seat_t *s2 = ptr2;
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return s1->id < s2->id ? -1
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: s1->id > s2->id ? 1
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: 0;
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}
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#endif
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int main()
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{
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int max=0;
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seat_t seats[input_sz];
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for(size_t i=0;i<input_sz;i++)
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{
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dlog("Testing %s\n", input[i]);
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seat_t seat = seats[i] = pbsearch(input[i]);
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int id = seat.id;
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dlog(" -> { .row = %d, .column = %d, .id = %d }\n", seat.row, seat.column, seat.id);
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if(id>max) max = id;
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}
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#ifdef PART2
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qsort(seats, input_sz, sizeof(seat_t), &_seat_cmp);
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for(size_t i=1; i<input_sz;i++)
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{
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seat_t prev = seats[i-1];
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seat_t this = seats[i];
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if( (this.id - prev.id) == 2)
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{
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printf("%d\n", prev.id+1);
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return 0;
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}
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}
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fprintf(stderr, "Failed to find id\n");
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return 1;
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#else
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printf("%d\n", max);
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#endif
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return 0;
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}
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