PAT-A1054 The Dominant Color 题目内容及题解

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 [0,2​24​​). 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

题目大意

题目给出一个数字方阵，从中找出占据主导地位的数字（数量超过一半），题目保证这样的数字必然存在。

解题思路

1. 按顺序逐个方阵，则设第一个数字为主导数字，当下一个数字与其相等时计数器加一，不相等时计数器减一；当计数器小于0时更新主导数字，计数器置1。因为必然存在数量超过一半的数，故照此法可以找到主导数字。
2. 输出主导数字并返回零值。

代码

#include<stdio.h>
int main(){
    int i,j,num,ans=-1,count=0;
    int M,N;
    scanf("%d%d",&M,&N);
    for(i=0;i<M;i++){
        for(j=0;j<N;j++){
            scanf("%d",&num);
            if(ans==num){
                count++;
            }else{
                count--;
                if(count<0){
                    ans=num;
                    count=1;
                }
            }
        }
    }
    printf("%d\n",ans);
    return 0;
}

运行结果