String pattern matching and insertion C++

I am trying to match and insert a patern in string.

Here in the Good peo Good peo and I am searching for peo and inserting ple.

But the Output is coming this:

Good people Good peo /n
Good peo Good people

I need to have output to be like

Good people Good people

My code:

#include<stdio.h>
#include<stdlib.h>

#include<iostream>
#include<string>
#include<string.h>
using namespace std;

int length(char s[])
{
    int len=0;
    int i=0;
    while(s[i]!='\0')
    {
        i++;
        len++;
    }
    return len;
}

void concatenate(char s1[], char s2[])
{
    int i=length(s1);
    int j=length(s2);
    int count=0;
    while(count<=j)
    {
        s1[i]=s2[count];
        i++;
        count++;
    }
}

void substring(char s[], char dest[], int ip, int len)
{
    int i=ip;
    int count=0;
    while(count<len)
    {
        dest[count]=s[i];
        count++;
        i++;
    }
    dest[count]='\0';
}

void ins(char T[], int ip, char P[])
{
    char temp1[100];
    char temp2[100];
    substring(T, temp1, 0, ip);
    substring(T, temp2, ip, length(T)-ip);
    concatenate(temp1, P);
    concatenate(temp1, temp2);
    T=temp1;
    cout<<T<<endl;
}

void del(char T[], int ip, int L)
{
    char temp1[100];
    char temp2[100];
    substring(T, temp1, 0, ip);
    substring(T, temp2, ip+L, length(T)-ip-L);
    concatenate(temp1, temp2);
    T=temp1;
    cout<<T<<endl;
}

//where T is the original string and P is the pattern to be deleted whereever it appears in the original string.
void delpat(char T[], char P[])
{
    char temp[100];
    for(int i=0; i<=length(T); i++)
    {
        substring(T, temp, i, length(P));
        if(strcmp(temp, P)==0)
            del(T, i, length(P));
    }
}

//where T is the original string, Q is the pattern to be inserted and P is the pattern after which it is inserted.
void inspat(char T[], char P[], char S[])
{
    char temp[100];
    for(int i=0; i<=length(T); i++)
    {
        substring(T, temp, i, length(P));
        if(strcmp(temp, P)==0)
            ins(T, i+length(P), S);
    }
}

int main()
{ char a[100];
    char T[]="Good peo Good peo";
    char P[]="peo";
    char S[]="ple";
    inspat(T, P, S);
    gets(a);
}