C——letterCounter

/* 一个统计字母（含大小写）出现次数的C程序 */
#include <stdio.h>

int main() {
    char counts[];
    char ch;

    /* initialization */
    for(int i = ; i < sizeof(counts)/sizeof(counts[]); i++) {
        counts[i] = ;
    }

    /* EOF: ctrl+D */
    while((ch = getchar()) != EOF) {
        if(ch >=  && ch <= ){
            counts[ch-]++;
        } else if (ch >=  && ch <= ) {
            counts[ch-+]++;
        }
    }

    for(int i = ; i < ; i++) {
        if(counts[i] != ) {
            printf("%c: %d\n", i+, counts[i]);
        }
    }

    for(int i = ; i < ; i++) {
        if(counts[i] != ) {
            printf("%c: %d\n", i+-, counts[i]);
        }
    }

    return ;
}

gcc letterCounter.c -o letterCounter.out

编译生成可执行文件

./letterCounter.out < letterCounter.c

将letterCounter.c源文件重定向输入到可执行程序中，查看字母出现频率