c++ - USACO-beads，无法调试 while 循环

Question

This是我正在研究的问题

我没有收到任何编译时错误、运行时错误，而且我的大部分代码似乎都可以正常工作。调试后，我发现 left() 和 right() 中的 while 循环导致了问题。我很难弄清楚为什么，所以任何帮助都会很棒。谢谢。

以防万一--

Sample input:

29

wwwbbrwrbrbrrbrbrwrwwrbwrwrrb

Sample output:

11

代码:

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1000000 + 10;
int n;
char cur_beads[MAXN];

//WORKS LIKE A BOSS:
void final_array(int int_in, char * array_in){

    for (int i = 1; i <= int_in; i++){
        cur_beads[n-i] = array_in[int_in - i];
    }

    for (int i = 0; i < n - int_in; i++){
        cur_beads[i] = array_in[int_in+i];
    }
//    cout << "new array, for "<< int_in << " = " <<cur_beads << endl << endl;;
}
//ERROR HERE:
int left(){ //function
    int left_a = 0, left_b = 0, c = 0;

    cout << cur_beads << endl;

    while((cur_beads[c] != 'b' || cur_beads[c] != 'w') &&  c <= n){
        cout << cur_beads[c] << endl;
        c++;
    }
    cout << "c = " << c << endl;
    while((cur_beads[c] == 'b' || cur_beads[c] == 'w')){
        left_b++;
        c++;
    }
    cout << "left_b = " << left_b << endl;

    c = 0;
    while((cur_beads[c] != 'r' || cur_beads[c] != 'w') &&  c <= n){
        c++;
    }
    cout << "c = " << c << endl;

    while(cur_beads[c] == 'r' || cur_beads[c] == 'w'){
        left_a++;
        c++;
    }
    cout << "left_a = " << left_a << endl;

    if (left_a > left_b){
        return left_a;
        cout << "left = " << left_a << endl;
    }
    else{
        return left_b;
        cout << "left = " << left_b << endl;
    }
}
//ERROR HERE:
int right(){ //function
    int right_a = 0, right_b = 0, c = 0;

    while((cur_beads[n-c] != 'b' || cur_beads[n-c] != 'w') &&  c <= n){
        c++;
    }
    while((cur_beads[n-c] == 'b' || cur_beads[n-c] == 'w')){
        right_b++;
        c++;
    }

    c = 0;
    while((cur_beads[n-c] != 'a' || cur_beads[n-c] != 'w') &&  c <= n){
        c++;
    }
    while((cur_beads[n-c] == '' || cur_beads[n-c] == 'w')){
        right_a++;
        c++;
    }

    if (right_a > right_b){
        return right_a;
        cout << "right = " << right_a << endl;
    }
    else{
        return right_b;
        cout << "right = " << right_b << endl;
    }
}

int main(){
    int ans = 0, current_ans = 0; //stored as 0 by default

    ifstream fin("beads.in");
    ofstream fout("beads.out");

    fin >> n;

    char beads[MAXN];


    for(int i = 0; i < n; i++){
        fin >> beads[i];
    }

//    final_array(11, beads);
//    current_ans = left();
//    cout << "current_ans = " << current_ans << endl;


    for(int i = 1; i < n; i++){ //main loop
        final_array(i, beads);
        current_ans = left() + right();
        cout << "current_ans = " << current_ans << endl;

        if (current_ans > ans){
            ans = current_ans;
        }
    }

    fout << ans << endl;

}

left() 中的所有 cout 都用于调试代码。

Answer 1

线

while((cur_beads[c] != 'b' || cur_beads[c] != 'w') &&  c <= n)

没有意义，因为任何字符都不会既是“b”又是“w”。更有意义的是将此行(以及其他有此问题的行)修改为

while((cur_beads[c] != 'b' && cur_beads[c] != 'w') &&  c <= n)