使用c语言生成概率统计函数库

1. 随机数生成函数

#include <stdlib.h>
#include <time.h>

void initRand() {
    srand(time(NULL));
}

int randInt(int min, int max) {
    return rand() % (max - min + 1) + min;
}

double randDouble(double min, double max) {
    return (double)rand() / RAND_MAX * (max - min) + min;
}

2. 统计函数

#include <stdio.h>

int countChar(const char* str, char c) {
    int count = 0;
    while (*str) {
        if (*str == c) {
            count++;
        }
        str++;
    }
    return count;
}

int countWord(const char* str) {
    int count = 0;
    while (*str) {
        if (*str == ' ' || *str == '\n' || *str == '\t') {
            count++;
        }
        str++;
    }
    return count;
}

int countLine(const char* str) {
    int count = 0;
    while (*str) {
        if (*str == '\n') {
            count++;
        }
        str++;
    }
    return count;
}

int countDigit(int n) {
    int count = 0;
    while (n) {
        count++;
        n /= 10;
    }
    return count;
}

int countPrime(int n) {
    if (n <= 1) {
        return 0;
    }
    for (int i = 2; i <= n / 2; i++) {
        if (n % i == 0) {
            return 0;
        }
    }
    return 1;
}

3. 概率函数

#include <math.h>

double normalPDF(double x, double mu, double sigma) {
    return exp(-pow(x - mu, 2) / (2 * pow(sigma, 2))) / (sqrt(2 * M_PI) * sigma);
}

double normalCDF(double x, double mu, double sigma) {
    return (1 + erf((x - mu) / (sigma * sqrt(2)))) / 2;
}

double binomialPDF(int k, int n, double p) {
    int c = 1;
    for (int i = 1; i <= k; i++) {
        c *= n - i + 1;
        c /= i;
    }
    return c * pow(p, k) * pow(1 - p, n - k);
}

double binomialCDF(int k, int n, double p) {
    double cdf = 0;
    for (int i = 0; i <= k; i++) {
        cdf += binomialPDF(i, n, p);
    }
    return cdf;
}

double uniformPDF(double x, double a, double b) {
    if (x < a || x > b) {
        return 0;
    }
    return 1 / (b - a);
}

double uniformCDF(double x, double a, double b) {
    if (x < a) {
        return 0;
    }
    if (x >= b) {
        return 1;
    }
    return (x - a) / (b - a);
}

4. 示例代码

#include <stdio.h>
#include "stats.h"

int main() {
    initRand();

    // 随机数生成
    printf("randInt(1, 10): %d\n", randInt(1, 10));
    printf("randDouble(0, 1): %f\n", randDouble(0, 1));

    // 统计函数
    printf("countChar(\"hello world\", 'l'): %d\n", countChar("hello world", 'l'));
    printf("countWord(\"hello world\\nhi there\\n\"): %d\n", countWord("hello world\nhi there\n"));
    printf("countLine(\"hello world\\nhi there\\n\"): %d\n", countLine("hello world\nhi there\n"));
    printf("countDigit(12345): %d\n", countDigit(12345));
    printf("countPrime(7): %d\n", countPrime(7));

    // 概率函数
    printf("normalPDF(0, 0, 1): %f\n", normalPDF(0, 0, 1));
    printf("normalCDF(1, 0, 1): %f\n", normalCDF(1, 0, 1));
    printf("binomialPDF(2, 5, 0.5): %f\n", binomialPDF(2, 5, 0.5));
    printf("binomialCDF(2, 5, 0.5): %f\n", binomialCDF(2, 5, 0.5));
    printf("uniformPDF(0.5, 0, 1): %f\n", uniformPDF(0.5, 0, 1));
    printf("uniformCDF(0.5, 0, 1): %f\n", uniformCDF(0.5, 0, 1));

    return 0;
}