# Monte Carlo Approximation of PI

Monte Carlo method for computing π is to draw a circle inscribed in a square, and randomly place dots in the square. The ratio of dots inside the circle to the total number of dots will approximately equal π/4.

![](https://upload.wikimedia.org/wikipedia/commons/8/84/Pi_30K.gif?1514455240021)

```c
#include stdio.h
#include stdlib.h
#include stdbool.h
#include ctype.h
#include string.h


bool isInteger(char s, bool accept_neg) {
    int i = 0;
    s[strlen(s)] = '0';
    if (accept_neg && i  strlen(s) && s[0] == '-') i++;
    for (; i  strlen(s); i++) {
        if (!isdigit(s[i])) return false;
    }
    return true;
}

char  get_input() {
    printf(Enter the number of iterations to run );
    char input[250];
    scanf(%[^n],input);
}

int getNIter() {
    while (1) {
        printf(Enter the number of iterations to run );
        char input[250];
        scanf(%[^n],input);
        input[strlen(input)] = 'n';

        if (isInteger(input, false)) {
            return atoi(input);
        }
    }
}

int getSeed() {
    while (1) {
        printf(Enter the seed for the random number generator );
        char input[250];
        scanf(%[^n],input);
        input[strlen(input)] = '0';

        if (isInteger(input, false)) {
            return atoi(input);
        }
        free(input);
    }
}

double gen_rand() {
    double High = 1.00;
    double Low = -1.00;
    return Low + (((double)rand())  (((double)RAND_MAX)  (High - Low)));
}

bool isInCircle(double x, double y) {
    return ((xx) + (yy)) = 1;
}

void runSimulation(int userSeed, int runIteration) {
    double mPoints = 0;
    srand(userSeed);
    for (int i = 0; i  runIteration; ++i) {
        if (isInCircle(gen_rand(), gen_rand())) {
            mPoints++;
        }
    }

    double piValue = (mPoints  (double)runIteration  4);
    printf(The value of pi is %.3lf.n, piValue);
}


int main() {

    int userSeed = getSeed();
    int nIter = getNIter();
    runSimulation(userSeed, nIter);

    fflush(stdin);
    getchar();
    return 0;
}
```


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