我该如何计算出现在数组多少？ [英] How do I count the number of occurrences in an array?

问题描述

我已生成的5个随机整数1-5的阵列。这里是数组看起来像现在： myArray的[5] = {3,3，1，4，5}

I have generated an array of 5 random integers from 1-5. Here is what the array looks like now: myArray[5] = {3, 3, 1, 4, 5}

我现在已经整理5的整数按升序排列数组，从最低到最高。

I have now sorted the array of 5 integers in ascending order, from least to greatest.

myArray的[5] = {1，3，3，4，5}

我现在需要统计出现特定的整数拥有的数量，使得它的一个表。

I now need to count the number of occurrences a specific integer has and make a table of it.

如：

Number: Count: 
1:1 
2:0 
3:3 
4:0 
5:1

我已经得到已通过数组循环最远。我有一个很难塔灵的数量和创造是如何匹配的字符串有一个计数。

The farthest I've gotten has been looping through the array. I am having a hard time talling the numbers and creating a count of how many occurances there are.

不使用任何地图，或迭代，等我试图让这个计数。以下是我已经尝试已经：

Not using any maps, or iterations, etc. I am trying to get this count. Here is what I have tried already:

int counts[10];

for (int x = 0; x <= 10; x++){
    int counter = 0;
    for (int j = 0; j < ARRAY_SIZE; j++){
        if (x == myArray[j]){
            counts[x] == counter++;
        }
    }

    cout << "Number: " << x << "Number of Occurances: " << counts[counter]<< "\n";
}

不过，我的输出是令人难以置信的错误。

However, my output is incredibly wrong.

推荐答案

使用的std ::地图来整数映射到自己的罪名。

Use a std::map to map integers to their counts.

std::map<int, int> counts;
for (int i = 0; i < 5; i++) {
    counts[myArray[i]]++; // increment the counter for the current value
}

现在您可以打印键和值计数。见如何通过一个C ++地图如何做这个循环。

Now you can print the keys and values in counts. See How to loop through a c++ map for how to do this.

您可以用数组，而不是地图做。唯一的区别是，它不会自动扩展处理更大的值（除非你使用的malloc 和的realloc 制作它动态调整）。

You can do it with an array instead of a map. The only difference is that it won't automatically expand to handle larger values (unless you use malloc and realloc to make it dynamically sized).

#define MAX_VALUE 9
int counts[MAX_VALUE+1] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
for (int i = 0; i < ARRAY_SIZE; i++) {
    if (myArray[i] <= MAX_VALUE) {
        counts[myArray[i]]++; // increment the counter for the current value
    }
}
for (int j = 0; j <= MAX_VALUE; j++) {
    cout << "Number: " << j << "Number of Occurances: " << counts[j] << endl;
}

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