题目：

题解：

int titleToNumber(char* columnTitle) {
    int number = 0;
    long multiple = 1;
    for (int i = strlen(columnTitle) - 1; i >= 0; i--) {
        int k = columnTitle[i] - 'A' + 1;
        number += k * multiple;
        multiple *= 26;
    }
    return number;
}