PAT甲级 1054 The Dominant Color (送分题)

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.

Sample Input:

5 3
0 0 255 16777215 24
24 24 0 0 24
24 0 24 24 24

Sample Output:

24

可以使用vector来存储不为0的颜色，这样就不用遍历所有的2²⁴个颜色了，遍历的都是有用的信息

#include 
#include 
using namespace std;
int num[16*1024*1024+1]={0};
vector<int> v; 
int main()
{
	int M,N,t;
	cin>>M>>N;
	for(int i=0;i<N;i++)
	{
		for(int j=0;j<M;j++)
		{
			scanf("%d",&t);
			if(num[t]==0)
				v.push_back(t);
			num[t]++;	
		}		
	}
	int maxn=-1,ans=-1;
	vector<int>::iterator it;
	for(it=v.begin();it!=v.end();it++)
	{
		if(num[*it]>maxn)
		{
			maxn=num[*it];
			ans=*it;	
		}
	}
	printf("%d\n",ans);		
	return 0;
}