题目：
题解：
cpp
int minMutation(char * start, char * end, char ** bank, int bankSize) {
int m = strlen(start);
int **adj = (int **)malloc(sizeof(int *) * bankSize);
int endIndex = -1;
for (int i = 0; i < bankSize; i++) {
adj[i] = (int *)malloc(sizeof(int) * bankSize);
memset(adj[i], 0, sizeof(int) * bankSize);
}
for (int i = 0; i < bankSize; i++) {
if (!strcmp(end, bank[i])) {
endIndex = i;
}
for (int j = i + 1; j < bankSize; j++) {
int mutations = 0;
for (int k = 0; k < m; k++) {
if (bank[i][k] != bank[j][k]) {
mutations++;
}
if (mutations > 1) {
break;
}
}
if (mutations == 1) {
adj[i][j] = 1;
adj[j][i] = 1;
}
}
}
if (endIndex == -1) {
return -1;
}
int *queue = (int *)malloc(sizeof(int) * bankSize);
bool *visited = (bool *)malloc(sizeof(bool) * bankSize);
memset(visited, 0, sizeof(bool) * bankSize);
int head = 0;
int tail = 0;
int step = 1;
for (int i = 0; i < bankSize; i++) {
int mutations = 0;
for (int k = 0; k < m; k++) {
if (start[k] != bank[i][k]) {
mutations++;
}
if (mutations > 1) {
break;
}
}
if (mutations == 1) {
queue[tail++] = i;
visited[i] = true;
}
}
while (head != tail) {
int sz = tail - head;
for (int i = 0; i < sz; i++) {
int curr = queue[head++];
if (curr == endIndex) {
for (int i = 0; i < bankSize; i++) {
free(adj[i]);
}
free(adj);
free(queue);
free(visited);
return step;
}
for (int j = 0; j < bankSize; j++) {
if (visited[j] || !adj[curr][j]) {
continue;
}
visited[j] = true;
queue[tail++] = j;
}
}
step++;
}
for (int i = 0; i < bankSize; i++) {
free(adj[i]);
}
free(adj);
free(queue);
free(visited);
return -1;
}