动态 Memory 分配中的问题

Question

I am writing a function to find peak in an array in a given range. I don't know the exact number of peaks in the given array. So I am using Dynamic memory allocation to store the peaks. The problem I am facing is that,

 int *findPeak(float *pArray, int length, int window, int *pCount) {
     int i, j ,count = 0, toPositive = 0, toNegative = 0;
     float peak;
     int *pPeakBuffer;
     bool firstZeroCross = false, toPositivePeak = false;
     int *peakBuffer = (int*)malloc(1*sizeof(int));
    
     for (i = 0; i < length; i += window) {
         if (count == 0) {
             peak = 0.0;
             for (j = i; j < window; j++) {
                 if (peak < pArray[j]) {
                     peak = pArray[j];
                     peakBuffer[count] = j;
                 }          
             }
             printf("Peak = %d\n\r", peakBuffer[count]);
             count++;
         }
         else {
             peak = 0.0;
             peakBuffer = (int*)realloc(peakBuffer, 1*sizeof(int)); 
             for (j = i; j < i+window; j++) {
                 if (peak < pArray[j]) {
                     peak = pArray[j];
                     peakBuffer[count] = j;             
                 }          
             }
             printf("Peak = %d\n\r", peakBuffer[count]);
             count++;
         }
     }
     *pCount = count;
     printf("count = %d\n\r", count);
     for (i = 0; i < count; i++)
         printf("%d ,", peakBuffer[i]);
     printf("\n\r");
     return peakBuffer;
 }

when a peak value is detected and it store it in the first memory. When the 2nd peak is detected it store in the 2nd memory, then the value in the first memory(previous memory) is changed to zero or other numbers and so on. Only the first and last peak is obtained. rest of the memory store some unknown values(not the peak value). I don't know why it is happening.

Answer 1

Apart from the memory allocation issues, and the boundary issues, and the "\n\r" misunderstanding, you've made an attempt worthy of what may be a helpful response.

It would take all day to dissect the code in your OP and discuss what's not quite right. Sorry.

The code below is adapted from yours, with issues sorted out and imposing what seems to be the objective of your pursuit. It seems that your code would have attempted to store the indices of successive increasing values found in any window... Really? That would be a lot of indices!!

This function searches for the single maximum value within any window and 'logs' only the indices (within the entire array, not just a 'window') of those maximums, one maximum for each window.

Perhaps this will provide you the functional foundation to achieve your objective. (I've compiled this, but have not tested it with any data. Offered "as is"...

int *findPeak( float *pArray, int length, int window, int *pCount ) {
    int i, count = 0;
    int *pPeaks = NULL; // ALWAYS initiase pointers

    for( i = 0; i < length; i += window ) {
        int peak = i; // assume peak is the first one in this window

        // scan window finding highest peak
        // Notice that 'j' starts with index of beginning of window
        // Notice limit to not run beyond length
        for( int j = i; j < i + window && j < length; j++ )
            if( pArray[ j ] > pArray[ peak ] ) // compare two floats values
                peak = j; // remember higher peak

        // get room to store this array index
        int *tmp = (int*)realloc( pPeaks, (count + 1) * sizeof *tmp );
        if( tmp == NULL ) {
            /* deal with failure */
            exit( EXIT_FAILURE );
        }
        pPeaks = tmp; // did not fail

        pPeaks[ count++ ] = peak; // index relative to entire array
    }

    // Pointless because this version will find one peak in each window
    // Could be calculated by dividing length by window
    *pCount = count;
    printf( "count = %d\n", *pCount );

    for( i = 0; i < count; i++ )
        printf( "%d, ", pPeaks[ i ] );
    putchar( '\n' );

    return pPeaks;
}