【C语言】将一个字符串插入至另一个源字符串的某个位置

前言

将一个字符串插入至另一个源字符串的某个位置

程序源码

#include <stdio.h>
#include <string.h>
char *insert(char *s1, char *s2, int n);
int main(void)
{
	char s1[50];
	char s2[50];
	int n;
	char *newstr;
	printf("请输入第一个字符串：");
	scanf("%s", s1);
	printf("请输入第二个字符串：");
	scanf("%s", s2);
	printf("请输入插入的位置：");
	scanf("%d", &n);
	newstr = insert(s1, s2, n);
	printf("%s\n", newstr);
	getchar();
	return 0;
}
char *insert(char *s1, char *s2, int n)
{
	int len1 = 0, len2 = 0, i, j = 0, k = 0;
	char s3[50];
	if (s1 == NULL)
		return NULL;
	if (s2 == NULL)
		return s1;
	len1 = strlen(s1);
	if(n > len1)
		return NULL;
	len2 = strlen(s2);
	for ( i = 0; i < n; i++) 
		j++; 
	for ( i = 0; i < len1; i++)
		s3[k++] = s1[i];
	for ( i = 0; i < len2; i++)
		s1[j++] = s2[i];
	for( i = n; i < len1; i++)
		s1[j++] = s3[i];
	s1[j] = '\0';
	return s1;
}

运行结果