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// 514. Freedom Trail
#include "leetcode.h"
/*
* in the video game fallout 4, the quest "road to freeom" requires players to
* reach a metal dial call the "freedom trail ring" and use the dial to spell a
* specific keyword to open the door. given a string 'rint' that represents the
* code engraved on the outer ring and another string 'key' that represents the
* keyword that needs to be spelled, return the minimum number of steps to spell
* all of the characters in the keyword. initially, the first character of the
* ring is aligned at "12:00" diretion. you should spell all the characters in
* 'key' one by rotating 'ring' clockwise or anticlockwise to make each
* character of the string aligned at the "12:00" direction and then by pressing
* the center button. at the stage of rotating the ring to spell the key
* character 'key[i]' you can rotate the ring clockwise or anticlockwise by one
* place, which counts as one step. the final purpose of the rotation is to
* align one of 'ring's characters at "12:00" direction, where this character
* must equal 'key[i]'
*/
int dp[101][101];
int dfs(char *ring, char *key, int ring_size, int key_size, int ring_idx,
int key_idx) {
if (key_idx == key_size)
return 0;
if (dp[key_idx][ring_idx] != -1)
return dp[key_idx][ring_idx];
int min_step = 1e9;
for (int i = 0; i < ring_size; i++)
if (ring[i] == key[key_idx]) {
int cw = (ring_idx + ring_size - i) % ring_size;
int ccw = (i + ring_size - ring_idx) % ring_size;
int step = fmin(cw, ccw) + 1 +
dfs(ring, key, ring_size, key_size, i, key_idx + 1);
min_step = fmin(min_step, step);
}
dp[key_idx][ring_idx] = min_step;
return min_step;
}
int findRotateSteps(char *ring, char *key) {
int ring_size = strlen(ring);
int key_size = strlen(key);
memset(dp, -1, sizeof(dp));
return dfs(ring, key, ring_size, key_size, 0, 0);
}
int main() {
char *r1 = "godding", *k1 = "gd", *r2 = "godding", *k2 = "godding";
printf("%d\n", findRotateSteps(r1, k1)); // expect: 4
printf("%d\n", findRotateSteps(r2, k2)); // expect: 13
}
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