C 函数从按递增顺序排序的数组中返回大于给定数字的最小数字的索引

Question

I am translating some code from Python to deepen my understanding of programming. I have got an array P_array with 1000 floating point numbers that are increscent. My task is to write a function that will return index of the first instance where P_array[x] is greater than 720. Here is both python and C code, I got stuck at last three lines of python code.

import numpy as np
import matplotlib.pyplot as plt

# Initializations

Dt = 1/32                              # timestep Delta t
P_init= 30                             # initial population
t_init = 0                              # initial time
t_end = 30                               # stopping time
n_steps = int(round(t_end/Dt))

t_array = np.zeros(n_steps+1)
P_array = np.zeros(n_steps+1)
t_array[0] = t_init
P_array[0] = P_init

#Eulers method

for i in range (1, n_steps + 1):
    P = P_array[i-1]
    t = t_array[i-1]
    dPdt = 0.7 * P * (1-(P/750)) - 20
    P_array[i] = P + Dt * dPdt
    t_array[i] = t + Dt

index = np.where(P_array>=720)

x = ([x[0] for x in index])
print (x)

C code

int main() {
    int i, j, x = 1;
    float dt, P_init, t_init, t_end;

    dt = 0.03125;
    P_init = 30;
    t_init = 0;
    t_end = 30;

    int n_steps = 0;
    n_steps = t_end/(float)dt;

    float Parray[n_steps+1];
    float Tarray[n_steps+1];

    for (i=0; i<n_steps+1; i++) {
       Parray[i]=0;
       Tarray[i]=0;
    }

    Parray[0] = P_init;
    Tarray[0] = t_init;

    float P,t,dpdt,s,d;

    while (x < n_steps+1) {
        P = Parray[x-1];
        t = Tarray[x-1];
        dpdt = 0.7 * P * (1-(P/750)) - 20;
        s = P + (dt * dpdt);
        Parray[x] = s;
        d = t + dt;
        Tarray[x] = d;
        x++;
        printf("%f  %f \n ",s,d);
    }

    return(0);
}

Answer 1

regarding: *C function that returns index of smallest number greater than given from increscent array`

the following proposed code:

1. performs the desired functionality

and now, the proposed code:

// C function that returns index of smallest number greater than given from increscent array

#include <stdio.h>

int main( void )
{
    //
    // assume code to generate array, sorted ascending
    size_t arraySize;
    float sortedArray[ arraySize ];
    //

    //
    // assume code to input target value
    float targetValue;
    //

    for( size_t i=0; i<arraySize; i++ )
    {
        if( targetValue > sortedArray[i] )
        {
            printf( "index into array = %zu\n", i );
            break;
        }
    }
}

Answer 2

thanks user3629249, this is my final code for loop, and it works perfectly.

    "double n = 720.00;
     int m = 0;

     for( j=0; j <n_steps+1; j++ ){

         if( n < Parray[j]){
             m = j;
             break;
         }
     }

      printf("%d\n", m);"