调整C++程序proDayoff数组赋值逻辑后输出异常求助

我是C++初学者，编写程序用于判断数组dayoffType每行的有效元素数量是否等于用户指定的dayoffLim值。初始代码输入8 31时，输出为0,0,0,3,4,5,0，符合预期。为得到3,4,5,0,0,0,0的输出，我修改了proDayoff数组的赋值索引逻辑，结果输入8 31时输出变为3,4,6,0,0,0,0，与预期不符，恳请帮忙排查问题。

初始代码 #

int dayoffLim = 0;
cin >> dayoffLim;   
int dayoffType[7][10] = {
                        {1, 2, 8, 9, 15, 16, 22, 23, 29, 30}, 
                    {2, 3, 9, 10, 16, 17, 23, 24, 30, 31}, 
                    {3, 4, 10, 11, 17, 18, 24, 25, 31, 0}, 
                    {4, 5, 11, 12, 18, 19, 25, 26, 0, 0}, 
                    {5, 6, 12, 13, 19, 20, 26, 27, 0, 0}, 
                    {6, 7, 13, 14, 20, 21, 27, 28, 0, 0},
                    {1, 7, 8, 14, 15, 21, 23, 28, 29, 0}
                };

    if(days == 28){
        int z = -1;
        for(int i=0; i<7; i++){
            int isDayoff = 0;
            for(int j=0; j<10; j++){
                if(dayoffType[i][j] <=28 && dayoffType[i][j] != 0){
                    isDayoff ++;
                }
            }
            
            if(isDayoff == dayoffLim){
                proDayoff[i] = i;
            }
            
        }
        
    }else if(days == 29){
        int z = -1;
        for(int i=0; i<7; i++){
            int isDayoff = 0;
            for(int j=0; j<10; j++){
                
                if(dayoffType[i][j] <=29 && dayoffType[i][j] != 0){
                    isDayoff ++;
                }
                
            }
            
            if(isDayoff == dayoffLim){
                proDayoff[i] = i;
            }
            
        }
            
    }else if(days == 30){
        int z = -1;
        for(int i=0; i<7; i++){
            int isDayoff = 0;
            for(int j=0; j<10; j++){
                
                if(dayoffType[i][j] <=30 && dayoffType[i][j] != 0){
                    isDayoff ++;
                }
            }
            
            if(isDayoff == dayoffLim){
                proDayoff[i] = i;
            }
            
        }
            
    }else if(days == 31){
        int z = -1;
        for(int i=0; i<7; i++){
            int isDayoff = 0;
            for(int j=0; j<10; j++){
                
                if(dayoffType[i][j] <=31 && dayoffType[i][j] != 0){
                    isDayoff ++;
                }
            }
            
            if(isDayoff == dayoffLim){
                proDayoff[i] = i;
            }
        }
    }

    
    for(int i=0; i<7; i++){
        cout << proDayoff[i] << " ";
    }

修改后的代码 #

int dayoffLim = 0, days = 0;
cin >> dayoffLim >> days;   
int dayoffType[7][10] = {
                        {1, 2, 8, 9, 15, 16, 22, 23, 29, 30}, 
                    {2, 3, 9, 10, 16, 17, 23, 24, 30, 31}, 
                    {3, 4, 10, 11, 17, 18, 24, 25, 31, 0}, 
                    {4, 5, 11, 12, 18, 19, 25, 26, 0, 0}, 
                    {5, 6, 12, 13, 19, 20, 26, 27, 0, 0}, 
                    {6, 7, 13, 14, 20, 21, 27, 28, 0, 0},
                    {1, 7, 8, 14, 15, 21, 23, 28, 29, 0}
                };


    if(days == 28){
        int z = -1;
        for(int i=0; i<7; i++){
            int isDayoff = 0;
            for(int j=0; j<10; j++){
                if(dayoffType[i][j] <=28 && dayoffType[i][j] != 0){
                    isDayoff ++;
                }
            }
            
                        //Where I adjust
            if(isDayoff == dayoffLim){
                z++;
            }
            proDayoff[z] = i;

            
        }
        
    }else if(days == 29){
        int z = -1;
        for(int i=0; i<7; i++){
            int isDayoff = 0;
            for(int j=0; j<10; j++){
                
                if(dayoffType[i][j] <=29 && dayoffType[i][j] != 0){
                    isDayoff ++;
                }
                
            }
            
                        //Where I adjust
            if(isDayoff == dayoffLim){
                z++;
            }
            proDayoff[z] = i;

            
        }
            

    }else if(days == 30){
        int z = -1;
        for(int i=0; i<7; i++){
            int isDayoff = 0;
            for(int j=0; j<10; j++){
                
                if(dayoffType[i][j] <=30 && dayoffType[i][j] != 0){
                    isDayoff ++;
                }
            }
            
                        //Where I adjust
            if(isDayoff == dayoffLim){
                z++;
            }
            proDayoff[z] = i;

            
        }
            
    }else if(days == 31){
        int z = -1;
        for(int i=0; i<7; i++){
            int isDayoff = 0;
            for(int j=0; j<10; j++){
                
                if(dayoffType[i][j] <=31 && dayoffType[i][j] != 0){
                    isDayoff ++;
                }
            }
            //Where I adjust
            if(isDayoff == dayoffLim){
                z++;
            }
            proDayoff[z] = i;
        }
    }

问题分析与解决 #

错误根源 #

修改后的代码中，无论当前行是否满足isDayoff == dayoffLim的条件，都会执行proDayoff[z] = i。以输入8 31为例：

1. 遍历到第3行（i=3）时，有效元素数为8，符合条件，z从-1递增到0，proDayoff[0] = 3，正确。
2. 遍历到第4行（i=4）时，有效元素数为8，符合条件，z递增到1，proDayoff[1] =4，正确。
3. 遍历到第5行（i=5）时，有效元素数为8，符合条件，z递增到2，proDayoff[2] =5，此时结果正确。
4. 遍历到第6行（i=6）时，有效元素数为9，不符合条件，z保持2不变，但代码依然执行proDayoff[2] =6，直接覆盖了之前的5，导致最终输出的第三个值变成6。

修复方案 #

将赋值操作移入if条件块内，仅当行符合条件时才更新proDayoff：

if(isDayoff == dayoffLim){
    z++;
    proDayoff[z] = i;
}

同时，建议初始化proDayoff数组为0，避免出现未定义的垃圾值：

int proDayoff[7] = {0};

修复后，输入8 31时，只有符合条件的第3、4、5行会被写入proDayoff的前三个位置，其余位置保持0，输出即为预期的3,4,5,0,0,0,0。

内容的提问来源于stack exchange，提问作者Chil