//判断第一个参数 是否 包含 第二个参数 1:包含 0:不包含
bool is_contain(std::string input_str,std::string input_find_str){
const char* s = input_str.c_str();
int count = input_find_str.size();const char* s1 = input_find_str.c_str();
int i, n =0;for(int i =0; i < input_str.size(); i++)if(s[i]== s1[0]){
int del =0;for(int j =1; j < count; j++){
if(s[i + j]== s1[j]){
del++;}}if(del == count -1){
n++;break;}}return n;}
判断字符串是否相等
//判断两个字符串相等
bool is_equal(std::string input_str1,std::string input_str2){
const char* s1 = input_str1.c_str();const char* s2 = input_str2.c_str();
int count1 = input_str1.size();
int count2 = input_str2.size();
int i, n =0;if(count1 == count2){
for(int i =0; i < count1; i++){
if(s1[i]!= s2[i]){
n =0;break;}
n =1;}}return n;}
保留小数点后几位
//保留几位小数std::string save_double_Several(double d, int num){
char char_s[20];
string str ="%."+to_string(num)+"f";sprintf(char_s, str.c_str(), d);
str = char_s;return str;}std::cout<<save_double_Several(3.1415926,2)<<std::endl;
double out =atof(save_double_Several(3.1415926,2));std::cout<<out<<std::endl;