题解 | #单词替换#

#include <stdio.h>
//求字符串长度：
int Length(char a[]) {
    int n = 0;
    for (int i = 0; a[i] != '\0'; i++) {
        n++;
    }
    return n;
}
int main() {
    char a[200] = "";
    char b[100] = "";
    char c[100] = "";
    while (gets(a)) {
        gets(b);
        gets(c);
        int len1 = Length(a);
        int len2 = Length(b);
        int len3 = Length(c);
        for (int i = 0; i < len1; i++) {
            len1 = Length(a);
            if (i == 0) {//由于开始没有空格，所以第一组词单独计算
                int j = 0, k = 0;
                while (a[k] == b[j] && j < len2) {
                    k++;
                    j++;
                }//第一组词前几个字与待替换词相同
                if (j == len2&&a[k]==' ') {//第一组词与待替换词完全相同
                    if (len2 == len3) {//长度相同，直接替换
                        for (int m = i, l = 0; l < len3; m++, l++) {
                            a[m] = c[l];
                        }
                    } else if (len2 > len3) {//待替换词长度大，直接将被替换词替换，计算两词相差长度number，将后续字符串向前移动number个距离
                        int m, l;
                        int number = len2 - len3;
                        for (m = i, l = 0; l < len3; m++, l++) {
                            a[m] = c[l];
                        }
                        while (a[m] != '\0') {
                            a[m] = a[m + number];
                            m++;
                        }
                    } else if (len2 < len3) {//被替换词长度大，将被替换词单独放进一个数组d，并将待替换词之后的字符串也移入d，再将d复制进a，打印数组a即可
                        char d[100] = "";
                        int q = 0;
                        for (int p = 0; p < len3; p++) {
                            d[q++] = c[p];
                        }
                        for (int w = len2; w < len1; w++) {
                            d[q++] = a[w];
                        }
                        int x = 0;
                        int len4 = Length(d);
                        for (int x = 0, y = 0; x < len4; x++, y++) {
                            a[x] = d[y];
                        }
                    }
                }
            } else if (a[i] == ' ') {//以空格为标识符，判断后续字符串
                int j = 0, k = i + 1;
                while (a[k] == b[j] && j < len2) {//该词组前几个字与待替换词相同
                    k++;
                    j++;
                }
                if (j == len2 && (a[k] == ' ' || k==len1)) {//该词组与待替换词完全相同，由于最后一组词后没有空格，所以用k=len1判断最后一组词
                    if (len2 == len3) {//长度相同，直接替换
                        for (int m = i + 1, l = 0; l < len3; m++, l++) {
                            a[m] = c[l];
                        }
                    } else if (len2 > len3) {//待替换词长度大，该词之前字符不做修改，直接将被替换词替换，计算两词相差长度number，将后续字符串向前移动number个距离
                        int m, l;
                        int number = len2 - len3;
                        for (m = i + 1, l = 0; l < len3; m++, l++) {
                            a[m] = c[l];
                        }
                        while (a[m] != '\0') {
                            a[m] = a[m + number];
                            m++;
                        }
                    } else if (len2 < len3) {//被替换词长度大，将待替换词之前的字符转移进数组d，被替换词依次进入数组d，并将待替换词之后的字符串也移入d，再将d复制进a，打印数组a即可
                        char d[100] = "";
                        int q = 0;
                        k = 0;
                        while (q <= i) {
                            d[q++] = a[k++];
                        }
                        for (int p = 0; p < len3; p++) {
                            d[q] = c[p];
                            q++;
                        }
                        for (int w = k + len2; w <= len1; w++) {
                            d[q] = a[w];
                            q++;
                        }
                        int x = 0;
                        int len4 = Length(d);
                        
                        for (int x = 0, y = 0; y < len4; x++, y++) {
                            a[x] = d[y];
                        }
                    }
                }
            }
        }
        printf("%s", a);
    }
    return 0;
}