3种解法

/**
 * NC86 矩阵元素查找
 */
public class NC86 {
  public int[] findElement(int[][] mat, int n, int m, int x) {
    // write code here
    int[] ans = new int[2];
    int i = n - 1;
    int j = 0;
    while (i >= 0 || j < m) {
      if (mat[i][j] == x) {
        ans[0] = i;
        ans[1] = j;
        return ans;
      } else if (mat[i][j] < x) {
        j++;
      } else {
        i--;
      }
    }
    return ans;
  }

  public int[] findElement0(int[][] mat, int n, int m, int x) {
    // write code here
    int[] ans = new int[2];
    for (int i = 0; i < n; i++) {
      int l = 0;
      int r = m - 1;
      while (l <= r) {
        int mi = l + ((r - l) >> 1);
        if (mat[i][mi] == x) {
          ans[0] = i;
          ans[1] = mi;
          return ans;
        } else if (mat[i][mi] < x) {
          l = mi + 1;
        } else {
          r = mi - 1;
        }
      }
    }
    return ans;
  }

  public int[] findElement1(int[][] mat, int n, int m, int x) {
    // write code here
    int[] ans = new int[2];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        if (mat[i][j] == x) {
          ans[0] = i;
          ans[1] = j;
          return ans;
        }
      }
    }
    return ans;
  }
}