C++ 字符串的 拼接，插入，查找与截取。

字符串的  拼接，插入，查找与截取。

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include<iostream>
#include<cmath>
#include<cstring>
#include<iostream>
#include<string.h>
#define MAX 1024
using namespace std;
char * A(char *s1, char*s2)
{
	strcat(s1, s2);
	return s1;
}



char * B(char *s1,int a,int b )
{
	char* buf = new char[MAX];
	
	int j = 0;
	for (int i = a; s1[i] && i < a+b; i++)
		buf[j++] = s1[i];
	buf[j] = '\0';
	strcpy(s1, buf);
	delete buf;
	return s1;
}

char* C(char* s1, char* s2, int a) {
	if (a > strlen(s1))
		return s1;

	char buf[2] = {0,0}, * p;
	char* buf1 = new char[MAX];
	buf[0] = s1[a];
	s1[a] = '\0';
	p = s1 + a + 1;
	strcpy(buf1, s1);	
	strcat(buf1, s2);
	strcat(buf1, buf);
	strcat(buf1, p);

	strcpy(s1, buf1);
	delete buf1;
	return s1;
}

int main()
{
	int n,a,b;
	cin >> n;
	char s1[1024];
	char s2[1024];
	char* p;
	getchar();
	cin >> s1;
	for (int i = 0; i < n; i++) {
		int k;
		cin >> k;
		switch (k)
		{
		case 1:
			getchar();
			cin >> s2;			
			cout << A(s1, s2) << endl;
			break;
		case 2:
			cin >> a >> b;
			cout << B(s1, a, b) << endl;
			break;
		case 3:
			cin >> a;
			getchar();
			cin >> s2;
			cout << C(s1, s2, a) << endl;
			break;
		case 4:		
			getchar();
			cin >> s2;
			p=strstr(s1, s2);
			if(p)
				cout << p - s1 << endl;
			else
				cout << -1 << endl;

		}
	}
	return 0;
}