1054 The Dominant Color (20分)

最新推荐文章于 2024-12-03 10:14:50 发布

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本文介绍了一种高效的算法，用于从图像中识别出占据面积超过一半的严格主导颜色。通过使用预设值和计数器，算法能在一次遍历中找出主导颜色，避免了传统方法的多次迭代和高计算成本。

Behind the scenes in the computer’s memory, color is always talked about as a series of 24 bits of information for each pixel. In an image, the color with the largest proportional area is called the dominant color. A strictly dominant color takes more than half of the total area. Now given an image of resolution M by N (for example, 800×600), you are supposed to point out the strictly dominant color.

Input Specification:

Each input file contains one test case. For each case, the first line contains 2 positive numbers: M (≤800) and N (≤600) which are the resolutions of the image. Then N lines follow, each contains M digital colors in the range [0,224). It is guaranteed that the strictly dominant color exists for each input image. All the numbers in a line are separated by a space.

Output Specification:

For each test case, simply print the dominant color in a line.

在复习408时看过的一种算法：设置一个pre值，如果当前值等于pre，那么计数器cnt+1，否则cnt-1，如果cnt减到0，那么令pre等于当前值。这样，如果有出现次数超过一半的值，一定是pre，因此，最终得到pre之后，需要再遍历一次输入值，判断pre出现次数是否超过一半。因为本题已经确认存在出现次数超过一半的值，所以就不需要再遍历判断了。

#include<iostream>
using namespace std;
int main() {
 int n, m, pre = -1, cnt = 1;
 cin >> n >> m;
 for (int i = 0; i < m; i++) {
  for (int j = 0; j < n; j++) {
   int d;
   cin >> d;
   if (d == pre)cnt++;
   else {
    cnt--;
    if (cnt == 0) {
     pre = d;
     cnt = 1;
    }
   }
  }
 }
 cout << pre << endl;
 return 0;
}