【算法专题十一】字符串

1. leetcode.14.最长公共前缀

1.1 题目

题目链接

1.2 思路

1.3 代码

class Solution {
public:string longestCommonPrefix(vector<string>& strs) {string ret = strs[0];for(int i = 0; i < strs.size(); i++){ret = HanShu(ret, strs[i]);}return ret;}string HanShu(string& s1, string& s2){int i = 0;while(i < min(s1.size(), s2.size()) && s1[i] == s2[i]){i++;}return s1.substr(0, i);}
};

2. leetcode.5.最长回文字串

2.1 题目

题目链接

2.2 思路

2.3 代码

class Solution {
public:string longestPalindrome(string s) {int begin = 0, len = 0;for(int i = 0; i < s.size(); i++){// 1. 先做奇数次遍历int left = i, right = i;while(left >= 0 && right < s.size() && s[left] == s[right]){left--;right++;if(right - left - 1 > len){begin = left + 1;len = right - left - 1;}}// 2. 再做偶数次遍历left = i, right = i + 1;while(left >= 0 && right < s.size() && s[left] == s[right]){left--;right++;if(right - left - 1 > len){begin = left + 1;len = right - left - 1;}}}return s.substr(begin, len);}
};

3. leetcode.67.二进制求和

3.1 题目

题目链接

3.2 思路

3.3 代码

class Solution {
public:string addBinary(string a, string b) {string ret;int cur1 = a.size() - 1, cur2 = b.size() - 1, t = 0;while(cur1 >= 0 || cur2 >= 0 || t > 0){if(cur1 >= 0) t += a[cur1--] - '0';if(cur2 >= 0) t += b[cur2--] - '0';ret += t % 2 + '0';t /= 2;}reverse(ret.begin(), ret.end());return ret;}
};

4. leetcode.43.字符串相乘

4.1 题目

题目链接

4.2 思路

4.3 代码

class Solution {
public:string multiply(string n1, string n2) {// 1. 首先进行 不进位相乘int m = n1.size(), n = n2.size();reverse(n1.begin(), n1.end());reverse(n2.begin(), n2.end());vector<int> tmp(m + n - 1);for(int i = 0; i < m; i++){for(int j = 0; j < n; j++){tmp[i + j] += (n1[i] - '0') * (n2[j] - '0');}}// 2. 处理进位string ret;int cur = 0, t = 0;while(cur < m + n - 1 || t != 0){if(cur < m + n - 1) t += tmp[cur++];ret += t % 10 + '0';t /= 10;}// 3. 处理前导0while(ret.size() > 1 && ret.back() == '0') ret.pop_back();reverse(ret.begin(), ret.end());return ret;}
};