DailyBuySellSelect

double[] prices = ... // your prices

int buy = 0; // index of 'buy' price
int sell = 0; // index 'sell' price

for(int i=0;i<prices.length;i++){
  if(prices[i]-prices[buy] > prices[sell] - prices[buy])
    sell = i;
  else if( prices[i] < prices[buy] ){
   buy = i;
   sell = i;
  }
}