Heart Beat sensing and displaying device

1#define samp_siz 4
2#define rise_threshold 4
3
4int sensorPin =  A0;
5
6#include <LiquidCrystal.h>
7LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
8
9void  setup() {
10    Serial.begin(9600);
11    lcd.begin(16, 2);
12    lcd.print("heart  rate: ");
13}
14
15void loop(){
16    float reads[samp_siz], sum;
17    long  int now, ptr;
18    float last, reader, start;
19    float first, second, third,  before, print_value;
20    bool rising;
21    int rise_count;
22    int n;
23    long int last_beat;
24
25    for (int i = 0; i < samp_siz; i++)
26      reads[i]  = 0;
27    sum = 0;
28    ptr = 0;
29
30    while(1)
31    {
32      n = 0;
33      start = millis();
34      reader = 0.;
35      do
36      {
37        reader  += analogRead(sensorPin);
38        n++;
39        now = millis();
40      }
41      while (now < start + 20);  
42      reader /= n;  
43      sum -= reads[ptr];
44      sum += reader;
45      reads[ptr] = reader;
46      last = sum / samp_siz;
47      
48      if (last > before)
49      {
50        rise_count++;
51        if  (!rising && rise_count > rise_threshold)
52        {
53          
54          rising=true;
55          first=millis()-last_beat;
56          last_beat=millis();
57          print_value=60000/(0.035*first  + 0.05*second + 0.1*third);
58          
59          delay(1500);
60          Serial.print(print_value/2);
61          Serial.print('\n');
62              
63          lcd.setCursor(0, 1);
64          lcd.print(print_value/ 2); 
65          
66          third = second;
67          second = first;
68          
69        }
70      }
71      else
72      {
73        rising = false;
74        rise_count = 0;
75      }
76      before  = last;
77      
78      
79      ptr++;
80      ptr %= samp_siz;
81    }
82      
83}
84