This is the code for AmiBroker but I think it can be easily translated into MQL4:
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reverse = Param ("reverse %" ,0.1, 0.1, 1,0.1)/100;

// initialize first element

j = 0;
KC[j] = Close[0];
direction=0;
for( i = 1; i < BarCount-1; i++ )
{
// percent reversal requirement
if(direction[j]==0)
{
if( Close[i] <= KC[j]) //continue down
{
KC[j] = Close[i];
}
else
{
if( Close[i] >= KC[j]*(1 + Reverse)) //Change direction to up
{
j++;
direction[j] = 1;

KC[j] = Close[i];
}
}
}
else
{
if( Close[i] >= KC[j]) //Continue up
{
KC[j] = Close[i];
}
else
{
if( Close[i] <= KC[j]*(1 - Reverse)) //Change direction to down
{
j++;
direction[j]=0;
KC[j] = Close[i];
}
}
}
}
delta = BarCount - j-1; //shift the chart to the wright

kagi= Ref(kc,-delta);
direction = Ref(direction,-delta);

Color =39;// IIf(kagi>Ref(kagi,-1), colorGreen, colorRed);

Plot(kagi, "", Color, styleStaircase|1024 );