题目：

题解：

typedef struct {int val;struct TreeNode *node;struct queNode *next;
} queNode;void init(queNode **p, int val, struct TreeNode *node) {(*p) = (queNode *)malloc(sizeof(queNode));(*p)->val = val;(*p)->node = node;(*p)->next = NULL;
}int minDepth(struct TreeNode *root) {if (root == NULL) {return 0;}queNode *queLeft, *queRight;init(&queLeft, 1, root);queRight = queLeft;while (queLeft != NULL) {struct TreeNode *node = queLeft->node;int depth = queLeft->val;if (node->left == NULL && node->right == NULL) {return depth;}if (node->left != NULL) {init(&queRight->next, depth + 1, node->left);queRight = queRight->next;}if (node->right != NULL) {init(&queRight->next, depth + 1, node->right);queRight = queRight->next;}queLeft = queLeft->next;}return false;
}