贡献两道简单的leetcode

111.Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

class Solution {
public:
    int minDepth(TreeNode* root) {
        if(root==NULL) return 0;
        if(root->left!=NULL && root->right==NULL) return  minDepth(root->left)+1;
        if(root->left==NULL && root->right!=NULL) return  minDepth(root->right)+1;
       
        int lefthight=minDepth(root->left);
        int righthight=minDepth(root->right);
        
        return lefthight<righthight?lefthight+1:righthight+1;
        
    }
};

14.Write a function to find the longest common prefix string amongst an array of strings.

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        bool flag=true;
        int count=0;
        char p;
        string prefix="";
        if(strs.size()==0) return prefix;
        if(strs.size()==1) return strs[0];
        
        while(flag)
        {
            p=strs[0][count];
            if(p==NULL) flag=false;
            
            for(int i=1; i<strs.size()&& flag ;i++)
            {
               if( count==strs[i].size() ||  p!=strs[i][count] ) flag=false; //若遍历到最短字符的最后一个 或者产生了不相等
                    
            }
            //cout<<"aaa"<<endl;
            count++;
            if(flag) prefix+=p;
            
        } 
        return prefix;
    }
};